The document discusses how genetic information flows from DNA to proteins. It explains that DNA is transcribed into mRNA through transcription, and mRNA is then translated into proteins through translation. During transcription, RNA polymerase makes a complementary mRNA copy of the DNA gene. During translation, transfer RNA (tRNA) molecules matching the mRNA codons bring amino acids to the ribosome, where they are linked together to form a protein chain according to the mRNA's genetic code. The protein then undergoes post-translational modifications before performing its function in the cell. Mutations can occur through changes in DNA bases that may alter protein sequences.
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
RNA splicing is a process where introns are removed from precursor messenger RNA (pre-mRNA) and exons are joined together to produce mature mRNA. It occurs in the nucleus and is essential for eukaryotes to produce proteins. The spliceosome, a large complex of RNA and proteins, facilitates two transesterification reactions that remove introns and ligate exons. RNA splicing generates protein diversity through alternative splicing and is important for cellular functions and disease processes.
Lampbrush chromosomes (LBCs) are very long chromosomes that are present in the egg cells of many vertebrates and invertebrates during meiosis. They have a central axis and appear brush-like due to the presence of many lateral loops of chromatin extending out perpendicular to the axis. RNA transcription occurs actively at the thin ends of the loops. LBCs provide favorable material for cytological studies due to their large size and distinct morphology during the prolonged meiotic prophase stage in egg cells. The loops represent individual chromatids and changes in their number and structure correlate with transcriptional activity and physiological processes in the organism.
RNA editing is a post-transcriptional process that makes discrete changes to RNA sequences. There are three main types of RNA editing: cytosine to uracil deamination, adenine to inosine deamination, and guide RNA-mediated insertion/deletion of uridine bases. Cytidine deamination is site-specific and involves enzymes like cytidine deaminase. Adenine deamination occurs in RNA secondary structures and involves enzymes like ADAR. Guide RNA editing involves hybridization of RNA to guide RNA, cleavage by an endonuclease, addition of uridine by TuTase, and ligation. RNA editing increases protein diversity and is essential for organelle development in eukaryotes.
The document discusses the nucleosome model of chromosome structure. It describes how DNA wraps around histone proteins to form nucleosomes, which are the basic units of chromatin. Specifically:
- Nucleosomes consist of 146-166 base pairs of DNA wrapped around an octamer of core histone proteins H2A, H2B, H3, and H4.
- Linker histone H1 binds to the DNA as it enters and exits each nucleosome, forming a structure known as a chromatosome.
- Adjacent nucleosomes are joined by 10-80 base pairs of linker DNA. The histone proteins and DNA interact via ionic bonds between negatively charged DNA and positively charged residues on
The document discusses DNA denaturation and renaturation, including:
- Denaturation involves unwinding the DNA double helix into single strands through heating or chemical treatment, disrupting hydrogen bonds between base pairs. This increases UV absorption.
- Renaturation is the spontaneous rewinding of single strands back into the original double helix structure when denaturing conditions are removed, through base pairing of complementary strands.
- C0t curves plot the fraction of single strands renatured versus the product of DNA concentration and time, and can indicate the complexity and size of the original DNA sample based on renaturation rates. More complex DNA with more dissimilar sequences takes longer to renature
The base sequence information present in the gene (DNA) is copied into an RNA molecule, which directly participates in protein synthesis and provides information for amino acid sequence of the protein. This RNA molecule is called messenger RNA or mRNA. The process of production of RNA copy of a DNA sequence is called transcription; this reaction is catalyzed by DNA-directed RNA polymerase, or simply RNA polymerase.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
RNA splicing is a process where introns are removed from precursor messenger RNA (pre-mRNA) and exons are joined together to produce mature mRNA. It occurs in the nucleus and is essential for eukaryotes to produce proteins. The spliceosome, a large complex of RNA and proteins, facilitates two transesterification reactions that remove introns and ligate exons. RNA splicing generates protein diversity through alternative splicing and is important for cellular functions and disease processes.
Lampbrush chromosomes (LBCs) are very long chromosomes that are present in the egg cells of many vertebrates and invertebrates during meiosis. They have a central axis and appear brush-like due to the presence of many lateral loops of chromatin extending out perpendicular to the axis. RNA transcription occurs actively at the thin ends of the loops. LBCs provide favorable material for cytological studies due to their large size and distinct morphology during the prolonged meiotic prophase stage in egg cells. The loops represent individual chromatids and changes in their number and structure correlate with transcriptional activity and physiological processes in the organism.
RNA editing is a post-transcriptional process that makes discrete changes to RNA sequences. There are three main types of RNA editing: cytosine to uracil deamination, adenine to inosine deamination, and guide RNA-mediated insertion/deletion of uridine bases. Cytidine deamination is site-specific and involves enzymes like cytidine deaminase. Adenine deamination occurs in RNA secondary structures and involves enzymes like ADAR. Guide RNA editing involves hybridization of RNA to guide RNA, cleavage by an endonuclease, addition of uridine by TuTase, and ligation. RNA editing increases protein diversity and is essential for organelle development in eukaryotes.
The document discusses the nucleosome model of chromosome structure. It describes how DNA wraps around histone proteins to form nucleosomes, which are the basic units of chromatin. Specifically:
- Nucleosomes consist of 146-166 base pairs of DNA wrapped around an octamer of core histone proteins H2A, H2B, H3, and H4.
- Linker histone H1 binds to the DNA as it enters and exits each nucleosome, forming a structure known as a chromatosome.
- Adjacent nucleosomes are joined by 10-80 base pairs of linker DNA. The histone proteins and DNA interact via ionic bonds between negatively charged DNA and positively charged residues on
The document discusses DNA denaturation and renaturation, including:
- Denaturation involves unwinding the DNA double helix into single strands through heating or chemical treatment, disrupting hydrogen bonds between base pairs. This increases UV absorption.
- Renaturation is the spontaneous rewinding of single strands back into the original double helix structure when denaturing conditions are removed, through base pairing of complementary strands.
- C0t curves plot the fraction of single strands renatured versus the product of DNA concentration and time, and can indicate the complexity and size of the original DNA sample based on renaturation rates. More complex DNA with more dissimilar sequences takes longer to renature
The base sequence information present in the gene (DNA) is copied into an RNA molecule, which directly participates in protein synthesis and provides information for amino acid sequence of the protein. This RNA molecule is called messenger RNA or mRNA. The process of production of RNA copy of a DNA sequence is called transcription; this reaction is catalyzed by DNA-directed RNA polymerase, or simply RNA polymerase.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
Translation is the process by which proteins are synthesized from messenger RNA (mRNA) in eukaryotes, which are organisms with membrane-bound nuclei. Translation involves mRNA being decoded on ribosomes into a polypeptide chain. It occurs through three main steps - initiation, elongation, and termination. Initiation involves the small ribosomal subunit binding to the 5' end of mRNA and scanning for the start codon. Elongation is the sequential addition of amino acids specified by the mRNA codons. Termination occurs when a stop codon is reached and release factors cause the ribosome to dissociate and release the completed protein.
This document discusses the structure and function of chromatin. It begins with a history of chromatin discovery from 1878-1974. Chromatin is composed of DNA, histones, and non-histone proteins. There are two types of chromatin - heterochromatin, which is condensed and inactive, and euchromatin, which is less condensed and contains actively transcribed genes. Chromatin replicates during interphase and condenses further during mitosis. DNA is packaged into nucleosomes, which involve 147 base pairs of DNA wrapped around an octamer of histone proteins, and these compact to form chromatin fibers and chromosomes. The functions of chromatin include efficient DNA packaging, facilitating cell division, preventing chromosome breakage, and regulating gene expression.
DNA is a double-helix molecule that carries genetic instructions. It is composed of two strands of polynucleotides made up of nucleotides, each containing a nitrogenous base, sugar, and phosphate. The strands are stabilized by hydrogen bonds between complementary bases and base-stacking interactions. DNA can be denatured into single strands by elevated temperature, extreme pH, low salt concentrations, or chemicals that disrupt hydrogen bonding between strands. Denaturation temperature depends on factors like base composition and length. Renaturation occurs when double-stranded DNA is cooled under conditions that allow the strands to re-form hydrogen bonds and complementary base pairing.
Gene expression: Translation and TranscriptionCyra Mae Soreda
The document discusses gene expression and transcription. It defines gene expression as the process by which a gene's information is converted into functional molecules like proteins or RNA. Transcription is the first step, where RNA polymerase makes an RNA copy of the gene. In eukaryotes, the initial RNA copy undergoes processing like capping, polyadenylation, and splicing before becoming messenger RNA. The mRNA is then transported out of the nucleus and translated by ribosomes into a protein product.
Chromatin modulation and role in gene regulationZain Khadim
This document discusses chromatin modulation and its role in gene regulation. It describes how DNA is packaged into chromatin through winding around histone proteins to form nucleosomes. Chromatin exists in two forms - loosely packed euchromatin and tightly packed heterochromatin. Gene expression is regulated through chromatin remodeling by mechanisms like nucleosome disruption, sliding, and transfer mediated by protein complexes like SWI/SNF. Histone modifications through processes like acetylation and methylation also influence gene regulation by altering chromatin structure. Precise control of gene expression through such chromatin modulation is important for cellular adaptation and efficient use of cellular resources.
This Presentation will be helpful to undergraduate and postgraduate students of biology and biotechnology in understanding the significance of COT curves in determination of gene and genome complexity amoug various organisms
DNA repair mechanisms in prokaryotes involve direct repair, excision repair, and mismatch repair. Direct repair converts damaged nucleotides directly back to their original structure using enzymes like photolyase. Excision repair removes damaged sections of DNA through base excision repair which removes single damaged bases using glycosylases and AP endonucleases, or nucleotide excision repair which removes short oligonucleotides. Mismatch repair recognizes and fixes errors made during DNA replication by distinguishing the parental DNA strands and excising the newly synthesized strand containing mistakes.
1) Eukaryotic gene expression is regulated at multiple levels including transcription, chromatin structure, post-transcriptional processing, and translation.
2) Regulation allows for adaptation and tissue-specific gene expression during development. Key differences from prokaryotes include the lack of operons and more complex regulation in eukaryotes.
3) Gene expression can be regulated short-term through transcriptional control, as seen in yeast galactose-utilizing genes, or long-term for development through mechanisms like chromatin remodeling.
This document discusses the structures and functions of heterochromatin and euchromatin. Heterochromatin is tightly packed and transcriptionally inactive, found near centromeres and telomeres. Euchromatin is loosely packed and contains most actively transcribed genes. The basic unit of DNA packing is the nucleosome, which involves DNA wound around histone proteins. Heterochromatin and euchromatin differ in their genetic activity, location within chromosomes, and condensation levels during interphase.
The document discusses the C-value paradox, which is the lack of relationship between genome size and organism complexity. It provides data on the wide range of genome sizes across different taxonomic groups. Introns and exons are described, with exons comprising the coding sequences and introns being removed from transcripts by splicing. Alternative splicing can generate multiple protein isoforms from a single gene. Repeated sequences, including satellites, minisatellites, microsatellites, transposons, SINEs and LINEs comprise a large portion of eukaryotic genomes.
Maternal effects are the influences of a mothers genotype on the phenotype of her offspring. It results from the asymmetric contribution of the female parent to the development of zygotes.
In terms of chromosomal genes, both male and female parents contribute equally to the zygote. The female parent contributes to the zygotes initial cytoplasm and organelles. Sperm rarely contribute anything other than chromosomes. Therefore zygotic development begins within a maternal medium and hence the maternal cytoplasm directly affects zygotic development.
This document discusses various classes of transcriptional regulatory elements. It begins by introducing transcriptional regulation and the basic transcriptional machinery. It then discusses the different elements that make up promoters, including the core promoter and proximal promoter elements. It also covers distal regulatory elements such as enhancers, silencers, insulators, and locus control regions. Enhancers can activate transcription from far away and silencers can repress it. Insulators protect genes from neighboring influences. Locus control regions coordinate expression of entire gene clusters.
DNA replication involves the synthesis of new DNA strands through a semi-conservative process whereby each new molecule contains one old strand and one new strand synthesized using the old strand as a template. Key enzymes involved include helicase, which unwinds the DNA double helix, primase, which initiates DNA synthesis, and DNA polymerase, which catalyzes phosphodiester bond formation to elongate the new strands. Fidelity is maintained through proofreading mechanisms that remove incorrectly incorporated nucleotides and DNA repair pathways that correct errors made during replication.
This document provides an overview of RNA editing. It begins by defining RNA editing as any process that results in a change to an RNA transcript sequence compared to the DNA template, excluding splicing. It then discusses the two main types of editing - base modification and insertion/deletion. Key points include that editing occurs in the nucleus, mitochondria and chloroplasts; the mechanism of pan editing in kinetoplastids involving guide RNAs; and examples of A-to-I and C-to-U editing in humans. The document also summarizes a case study on the role of the SLO2 gene in plant stress responses through regulation of mitochondrial electron transport.
This document provides an overview of the central dogma of biology and DNA replication. It begins by defining the central dogma as the flow of genetic information from DNA to RNA to proteins. It then discusses the four requirements for DNA to be the genetic material and explains DNA replication through semi-conservative replication and starting at the origin. The basics of transcription and translation are also summarized, including the components and steps of each process.
The document summarizes DNA replication. It describes that DNA replication produces two identical copies of DNA from one original molecule through a semi-conservative process. This involves unwinding of DNA at origins of replication by helicase to form replication forks that grow bidirectionally. DNA polymerase then synthesizes new strands using the original strands as templates. Replication occurs through initiation, elongation, and termination steps mediated by various proteins at the replication fork. The Meselson-Stahl experiment provided evidence that DNA replication is semi-conservative through density gradient centrifugation of parental and progeny DNA.
Chromosome structure and packaging of dnaDIPTI NARWAL
Chromosomes are structures that contain DNA and help transmit genetic information from parents to offspring. They exist in the nucleus of cells and vary in number between species. DNA is packaged into chromosomes through histone proteins that allow very long DNA strands to fit inside cells. DNA wraps around histone proteins to form structures called nucleosomes, which contain 147 base pairs of DNA wrapped around an octamer of histone proteins. Nucleosomes further compact DNA by forming a beads-on-a-string structure that can coil and fold, allowing the long DNA molecules to fit within cells.
While carrying the Apo E gene does not necessarily mean you will develop disease, lifestyle factors like smoking, alcohol consumption, and high calorie diets can trigger expression if the E4 allele is present. Seeing a physician can provide individualized treatment and genetic testing to learn your status, which may include advice on lifestyle changes to reduce risks. Knowing your genetic status through testing allows for customized recommendations and counseling on reducing risks of cardiovascular and Alzheimer's diseases.
Recombinant DNA technology involves combining DNA segments to form new DNA molecules. In 1973, scientists Boyer and Cohen developed the technique by inserting DNA into a vector molecule that can then be introduced into host cells to replicate. This allows for large-scale production of human proteins in bacteria, such as insulin, growth hormones, and blood clotting factors. Safety measures like physical and biological containment are used to prevent accidental release of recombinant bacteria. While offering medical benefits, recombinant DNA technology does pose risks that must be carefully managed.
Translation is the process by which proteins are synthesized from messenger RNA (mRNA) in eukaryotes, which are organisms with membrane-bound nuclei. Translation involves mRNA being decoded on ribosomes into a polypeptide chain. It occurs through three main steps - initiation, elongation, and termination. Initiation involves the small ribosomal subunit binding to the 5' end of mRNA and scanning for the start codon. Elongation is the sequential addition of amino acids specified by the mRNA codons. Termination occurs when a stop codon is reached and release factors cause the ribosome to dissociate and release the completed protein.
This document discusses the structure and function of chromatin. It begins with a history of chromatin discovery from 1878-1974. Chromatin is composed of DNA, histones, and non-histone proteins. There are two types of chromatin - heterochromatin, which is condensed and inactive, and euchromatin, which is less condensed and contains actively transcribed genes. Chromatin replicates during interphase and condenses further during mitosis. DNA is packaged into nucleosomes, which involve 147 base pairs of DNA wrapped around an octamer of histone proteins, and these compact to form chromatin fibers and chromosomes. The functions of chromatin include efficient DNA packaging, facilitating cell division, preventing chromosome breakage, and regulating gene expression.
DNA is a double-helix molecule that carries genetic instructions. It is composed of two strands of polynucleotides made up of nucleotides, each containing a nitrogenous base, sugar, and phosphate. The strands are stabilized by hydrogen bonds between complementary bases and base-stacking interactions. DNA can be denatured into single strands by elevated temperature, extreme pH, low salt concentrations, or chemicals that disrupt hydrogen bonding between strands. Denaturation temperature depends on factors like base composition and length. Renaturation occurs when double-stranded DNA is cooled under conditions that allow the strands to re-form hydrogen bonds and complementary base pairing.
Gene expression: Translation and TranscriptionCyra Mae Soreda
The document discusses gene expression and transcription. It defines gene expression as the process by which a gene's information is converted into functional molecules like proteins or RNA. Transcription is the first step, where RNA polymerase makes an RNA copy of the gene. In eukaryotes, the initial RNA copy undergoes processing like capping, polyadenylation, and splicing before becoming messenger RNA. The mRNA is then transported out of the nucleus and translated by ribosomes into a protein product.
Chromatin modulation and role in gene regulationZain Khadim
This document discusses chromatin modulation and its role in gene regulation. It describes how DNA is packaged into chromatin through winding around histone proteins to form nucleosomes. Chromatin exists in two forms - loosely packed euchromatin and tightly packed heterochromatin. Gene expression is regulated through chromatin remodeling by mechanisms like nucleosome disruption, sliding, and transfer mediated by protein complexes like SWI/SNF. Histone modifications through processes like acetylation and methylation also influence gene regulation by altering chromatin structure. Precise control of gene expression through such chromatin modulation is important for cellular adaptation and efficient use of cellular resources.
This Presentation will be helpful to undergraduate and postgraduate students of biology and biotechnology in understanding the significance of COT curves in determination of gene and genome complexity amoug various organisms
DNA repair mechanisms in prokaryotes involve direct repair, excision repair, and mismatch repair. Direct repair converts damaged nucleotides directly back to their original structure using enzymes like photolyase. Excision repair removes damaged sections of DNA through base excision repair which removes single damaged bases using glycosylases and AP endonucleases, or nucleotide excision repair which removes short oligonucleotides. Mismatch repair recognizes and fixes errors made during DNA replication by distinguishing the parental DNA strands and excising the newly synthesized strand containing mistakes.
1) Eukaryotic gene expression is regulated at multiple levels including transcription, chromatin structure, post-transcriptional processing, and translation.
2) Regulation allows for adaptation and tissue-specific gene expression during development. Key differences from prokaryotes include the lack of operons and more complex regulation in eukaryotes.
3) Gene expression can be regulated short-term through transcriptional control, as seen in yeast galactose-utilizing genes, or long-term for development through mechanisms like chromatin remodeling.
This document discusses the structures and functions of heterochromatin and euchromatin. Heterochromatin is tightly packed and transcriptionally inactive, found near centromeres and telomeres. Euchromatin is loosely packed and contains most actively transcribed genes. The basic unit of DNA packing is the nucleosome, which involves DNA wound around histone proteins. Heterochromatin and euchromatin differ in their genetic activity, location within chromosomes, and condensation levels during interphase.
The document discusses the C-value paradox, which is the lack of relationship between genome size and organism complexity. It provides data on the wide range of genome sizes across different taxonomic groups. Introns and exons are described, with exons comprising the coding sequences and introns being removed from transcripts by splicing. Alternative splicing can generate multiple protein isoforms from a single gene. Repeated sequences, including satellites, minisatellites, microsatellites, transposons, SINEs and LINEs comprise a large portion of eukaryotic genomes.
Maternal effects are the influences of a mothers genotype on the phenotype of her offspring. It results from the asymmetric contribution of the female parent to the development of zygotes.
In terms of chromosomal genes, both male and female parents contribute equally to the zygote. The female parent contributes to the zygotes initial cytoplasm and organelles. Sperm rarely contribute anything other than chromosomes. Therefore zygotic development begins within a maternal medium and hence the maternal cytoplasm directly affects zygotic development.
This document discusses various classes of transcriptional regulatory elements. It begins by introducing transcriptional regulation and the basic transcriptional machinery. It then discusses the different elements that make up promoters, including the core promoter and proximal promoter elements. It also covers distal regulatory elements such as enhancers, silencers, insulators, and locus control regions. Enhancers can activate transcription from far away and silencers can repress it. Insulators protect genes from neighboring influences. Locus control regions coordinate expression of entire gene clusters.
DNA replication involves the synthesis of new DNA strands through a semi-conservative process whereby each new molecule contains one old strand and one new strand synthesized using the old strand as a template. Key enzymes involved include helicase, which unwinds the DNA double helix, primase, which initiates DNA synthesis, and DNA polymerase, which catalyzes phosphodiester bond formation to elongate the new strands. Fidelity is maintained through proofreading mechanisms that remove incorrectly incorporated nucleotides and DNA repair pathways that correct errors made during replication.
This document provides an overview of RNA editing. It begins by defining RNA editing as any process that results in a change to an RNA transcript sequence compared to the DNA template, excluding splicing. It then discusses the two main types of editing - base modification and insertion/deletion. Key points include that editing occurs in the nucleus, mitochondria and chloroplasts; the mechanism of pan editing in kinetoplastids involving guide RNAs; and examples of A-to-I and C-to-U editing in humans. The document also summarizes a case study on the role of the SLO2 gene in plant stress responses through regulation of mitochondrial electron transport.
This document provides an overview of the central dogma of biology and DNA replication. It begins by defining the central dogma as the flow of genetic information from DNA to RNA to proteins. It then discusses the four requirements for DNA to be the genetic material and explains DNA replication through semi-conservative replication and starting at the origin. The basics of transcription and translation are also summarized, including the components and steps of each process.
The document summarizes DNA replication. It describes that DNA replication produces two identical copies of DNA from one original molecule through a semi-conservative process. This involves unwinding of DNA at origins of replication by helicase to form replication forks that grow bidirectionally. DNA polymerase then synthesizes new strands using the original strands as templates. Replication occurs through initiation, elongation, and termination steps mediated by various proteins at the replication fork. The Meselson-Stahl experiment provided evidence that DNA replication is semi-conservative through density gradient centrifugation of parental and progeny DNA.
Chromosome structure and packaging of dnaDIPTI NARWAL
Chromosomes are structures that contain DNA and help transmit genetic information from parents to offspring. They exist in the nucleus of cells and vary in number between species. DNA is packaged into chromosomes through histone proteins that allow very long DNA strands to fit inside cells. DNA wraps around histone proteins to form structures called nucleosomes, which contain 147 base pairs of DNA wrapped around an octamer of histone proteins. Nucleosomes further compact DNA by forming a beads-on-a-string structure that can coil and fold, allowing the long DNA molecules to fit within cells.
While carrying the Apo E gene does not necessarily mean you will develop disease, lifestyle factors like smoking, alcohol consumption, and high calorie diets can trigger expression if the E4 allele is present. Seeing a physician can provide individualized treatment and genetic testing to learn your status, which may include advice on lifestyle changes to reduce risks. Knowing your genetic status through testing allows for customized recommendations and counseling on reducing risks of cardiovascular and Alzheimer's diseases.
Recombinant DNA technology involves combining DNA segments to form new DNA molecules. In 1973, scientists Boyer and Cohen developed the technique by inserting DNA into a vector molecule that can then be introduced into host cells to replicate. This allows for large-scale production of human proteins in bacteria, such as insulin, growth hormones, and blood clotting factors. Safety measures like physical and biological containment are used to prevent accidental release of recombinant bacteria. While offering medical benefits, recombinant DNA technology does pose risks that must be carefully managed.
The document summarizes the process of drug discovery and development. It involves several long steps: understanding the disease, finding a biological target, discovering a lead compound through screening or nature, conducting preclinical testing on animals, and then clinical trials in three phases with humans to test safety and efficacy before the FDA decides whether to approve the drug. The entire process from discovery to approval takes an average of 10-15 years and costs $1-2 billion. Drugs also have different categories depending on how they are regulated and prescribed.
This document summarizes key points about DNA mutation from a lecture and assigned readings. It discusses Gregor Mendel's discovery of the principles of heredity and inheritance through experiments with pea plants. It then explains how early geneticists like Thomas Hunt Morgan studied mutations by observing phenotypic changes in fruit flies. The document defines what constitutes a mutation and discusses how mutations occur at the DNA level. It distinguishes between mutations in somatic cells versus germ line cells and their differing implications. The document also covers topics like mutation rates, locations of mutations within genomes, and spontaneous mutations.
DNA controls protein synthesis by determining the sequence of amino acids that join together to form proteins. The DNA code uses three-nucleotide sequences or triplets to specify each amino acid. During protein synthesis, a complementary mRNA molecule is generated from DNA and transports the code to the cytoplasm. Transfer RNA then reads the mRNA code and delivers the corresponding amino acids to the ribosome, where they are joined into a polypeptide chain according to the DNA instructions. This process continues until a stop codon is reached, resulting in a fully-formed protein.
Proteins fold into complex 3D structures essential for their function. There are four levels of protein structure - primary, secondary, tertiary, and quaternary. Chaperone proteins help other proteins fold correctly to prevent aggregation. Misfolded proteins can result from changes in temperature, pH, or lack of chaperones and may lead to disease if not degraded. Normally, misfolded proteins are targeted for degradation by the ubiquitin proteasome pathway, but accumulation of misfolded proteins can cause conditions like Alzheimer's disease.
The document summarizes the mechanism of protein folding in 3 sentences:
Protein folding is the physical process by which a polypeptide folds into its characteristic three-dimensional structure, driven by hydrophobic amino acids forming a core shielded from water and polar residues interacting with surrounding water. Key factors that stabilize the folded state include intramolecular hydrogen bonds and hydrophobic interactions. Molecular chaperones assist in protein folding in the crowded intracellular environment to prevent misfolding and aggregation.
This document discusses oral hypoglycemic drugs and insulin used to treat diabetes. It describes the two main types of diabetes - type 1 caused by insulin deficiency and type 2 caused by insulin resistance. The document outlines several classes of oral hypoglycemic drugs including biguanides, sulfonylureas, meglitinides, thiazolidinediones, and alpha-glucosidase inhibitors. It provides details on the mechanism of action, pharmacokinetics, effects and side effects of drugs from each class.
The document discusses DNA, RNA, and protein synthesis. It describes key discoveries such as the Hershey-Chase experiment demonstrating that DNA is the genetic material. It explains the structure of DNA as a double helix with base pairing between strands. The process of DNA replication is summarized, including semi-conservative replication and the role of enzymes. Transcription of DNA to RNA and translation of RNA to protein are also summarized, with an overview of the central dogma of molecular biology.
The document discusses several key concepts in molecular biology:
1) Beadle and Tatum's experiments with Neurospora led to the one-gene, one-polypeptide hypothesis, which states that each gene directs the synthesis of a specific polypeptide.
2) DNA is transcribed into RNA, which is then translated into protein. Retroviruses reverse this process by transcribing RNA back into DNA.
3) The genetic code consists of triplets of nucleotides (codons) that specify which amino acid will be added during translation. There are 64 possible codons but only 20 different amino acids, so the genetic code is redundant.
4) Mutations in DNA
This document provides information about RNA, transcription, translation, and gene regulation. It begins by contrasting the structures of RNA and DNA, explaining the three main types of RNA, and describing the process of transcription. It then discusses the genetic code, how translation works using tRNAs and ribosomes to assemble amino acids into proteins, and the central dogma of molecular biology. The document concludes by covering gene regulation in prokaryotes and eukaryotes, including how operons control gene expression and how transcription factors regulate development.
This document provides an overview of gene expression from DNA to protein. It discusses how genes code for proteins, the process of transcription of DNA to mRNA, and translation of mRNA to amino acid sequences to form proteins. Key points covered include:
- Genes contain the code for proteins and a change in the gene results in a change to the protein's amino acid sequence.
- Transcription involves copying a gene's DNA sequence into a complementary mRNA sequence. Translation then converts the mRNA sequence into the amino acid sequence of a protein.
- The genetic code specifies which three-letter codon in mRNA corresponds to each amino acid. Translation uses this code to build proteins from mRNA instructions.
Brief Concepts and Questions EXAM 2 Chapter 8 DNA RNA Protein What i.pdfmckenziecast21211
Brief Concepts and Questions EXAM 2 Chapter 8: DNA RNA Protein What is DNA? a
phosphate Structure of DNA: Building blocks are called nucleotides Each nucleotide is
composed of three br uithofenas bee. What makes DNA so special? Provide 4 reasons, below
DNA DNA (Replication): Where does DNA replication take place? When does DNA replication
take place? Explain steps involved in DNA replication: DNA RNA Protein (Gene Expression)
Involves 2 processes: 1. Transcription 2. Translation Explain the Synthesis of Proteins (Gene
Expression): o DNA RNA Protein What is RNA? What is \"codon What is \"anticodon\" What is
a protein molecule? DNA mutation; Change in nucleotide bases of DNA Duplex Point mutation
Frame shift mutation
Solution
Question
Answer
Where does DNA replication take place:
It takes place in the nucleus in case of eukaryotic cells and in the cytoplasm in case of
prokaryotic cells
When does DNA replication take place:
DNA replication occurs during the S-phase during cell cycle, so that cell can make an extra copy
of genetic material.
Explain steps involved in DNA replication:
Initiation: During initiation, the proteins will bind to the origin of replication; helicase unwinds
the DNA helix which results in the formation of two replication forks.
Elongation: A RNA primer sequence will be added to this the DNA pol III will add the
nucleotides in 5’ to 3’ direction and chain will elongate.
Termination: In case of bacteria, termination of replication occurs whenever two replication
forks meet each other from the opposite end of the parental chromosome.
Transcription
Gene expression first step is transcription, here a particular segment of DNA will be copied into
RNA with the help of the enzyme RNA polymerase
Translation
Translation is the final step of the gene expression. Here mRNA will be used to synthesize the
polypeptide chain. The information present in the mRNA in the form of codon will code for the
amino acids needed for polypeptide chain synthesis.
What is RNA?
RNA is ribonucleic acid and is found in all living cells. It acts as the messenger carrying
instructions from DNA for the synthesis of proteins.
Few viruses will have RNA as their genetic material.
What is codon?
Codon is a sequence of three nucleotides and they together form a unit of genetic code in either
DNA or RNA.
What is anticodon?
It is found on tRNA and it is a sequence of three nucleotides which forms a genetic code on
tRNA, and these anticodon is complementary to the codons found on messenger RNA.
What is a protein molecule?
During translation, when amino acids are added in a sequential manner, the condensation of
amino acids will form a peptide bond in between them and finally forms a polypeptide chain. It
is the DNA through mRNA directs the protein synthesis.
Point mutation
In point mutation, only one or very few nucleotides will be affected or mutated in a gene
sequence.
Frame shift mutation
Either insertions or deletion can result in frame shift mutation, due to th.
The document summarizes key concepts about gene expression and regulation:
1. DNA contains genes that encode instructions for proteins; during transcription, genes are copied into mRNA which is then translated by ribosomes into proteins.
2. In eukaryotes, mRNA must carry DNA information from the nucleus to the cytoplasm for protein synthesis, since DNA is in the nucleus but protein synthesis occurs in the cytoplasm.
3. Transcription involves copying a gene into mRNA, which then directs ribosomes during translation to synthesize the encoded protein according to the genetic code where RNA codons specify amino acids.
This document provides information about RNA, transcription, translation, and gene regulation. It begins by contrasting the structures of RNA and DNA, explaining the three main types of RNA, and the process of transcription. It then discusses the genetic code, how translation works using tRNA and rRNA, and the central dogma of molecular biology. The document concludes by covering gene regulation in prokaryotes and eukaryotes, including how operons and transcription factors control gene expression to allow cell specialization.
This document summarizes key concepts in microbial genetics including:
1) Plasmids exist separately from bacterial chromosomes and can transfer genes horizontally.
2) The central dogma of molecular biology describes how DNA is transcribed into RNA and translated into protein.
3) Bacterial gene expression is regulated through operons such as the lac and tryptophan operons which are induced or repressed in response to environmental conditions.
4) Mutations can occur spontaneously or be caused by mutagens and can alter bacterial genes and phenotypes.
The central dogma of molecular biology describes the flow of genetic information within cells. It states that information flows from DNA to RNA to protein, but not in the reverse direction. The document then provides more details about DNA replication, transcription, and translation. It explains the basic structures and processes involved, including the key enzymes and molecules. Examples are given of prokaryotic and eukaryotic differences. The lac operon is used as an example of transcriptional control in response to environmental signals.
From DNA to Protein
1. DNA contains genes that provide instructions for building proteins through transcription and translation. RNA is produced through transcription and carries the genetic code from DNA. There are three main types of RNA: mRNA, rRNA, and tRNA.
2. During translation, mRNA attaches to ribosomes where tRNA brings amino acids to add to the growing polypeptide chain according to the mRNA codons until a stop codon is reached. This process synthesizes proteins using the genetic code stored in DNA.
3. Mutations in DNA can occur through changes in single nucleotides or the insertion/deletion of nucleotides. This can alter the mRNA and resulting protein sequence produced.
The document summarizes the process of gene expression from DNA to protein. It discusses how genes provide the code for proteins, the central dogma of DNA to RNA to protein, the types and roles of RNA including mRNA, tRNA and rRNA. It then explains the steps of transcription, processing of mRNA, translation, the genetic code and the role of transfer RNA and ribosomes in protein synthesis.
DNA and RNA both contain nucleotides with sugars, bases, and phosphates. DNA contains deoxyribose and thymine, while RNA contains ribose and uracil. DNA exists as two strands, while RNA exists as a single strand. The genetic code uses three-base sequences called codons to specify the twenty amino acids. Transcription produces mRNA from DNA, and translation uses mRNA, tRNA, ribosomes and amino acids to assemble polypeptides specified by mRNA codons. Originally it was believed one gene specified one polypeptide, but exceptions to this rule have been discovered.
DNA replication is the process by which a cell makes an identical copy of its DNA before cell division. It involves unwinding the DNA double helix and using each strand as a template to create a new partner strand through complementary base pairing. DNA polymerase adds nucleotides to the new strands to replicate the DNA. This ensures each daughter cell has an exact copy of the original DNA.
Gene expression occurs in two steps: transcription and translation. In transcription, RNA polymerase copies information from DNA to mRNA. In translation, mRNA directs ribosomes to assemble a polypeptide chain from amino acids based on the genetic code. The central dogma of molecular biology states that DNA is transcribed into RNA which is then translated into protein.
The document summarizes key concepts about DNA, RNA, and protein synthesis. It discusses:
1) The structure of DNA as a double helix with nucleotides containing nitrogen bases that allow the strands to replicate.
2) Chromosomes contain DNA and package it tightly for storage in eukaryotic cells. DNA replication results in two DNA molecules each with one original and one new strand.
3) RNA acts as a messenger to transfer DNA instructions to the cell. Transcription and translation lead to protein synthesis on ribosomes according to the genetic code.
4) Mutations can occur through changes to nucleotides and can impact protein function, though most do not affect the organism.
DNA replication is the process by which a cell makes an identical copy of its DNA before cell division. It involves unwinding the DNA double helix and using each strand as a template to create a new partner strand. DNA polymerase adds complementary nucleotides to each new strand. When complete, the process generates two identical DNA double helices from the original. Before a cell divides, it must replicate its DNA so that the resulting daughter cells have the same genetic information as the parent cell.
The document describes the central dogma of molecular biology, which is the flow of genetic information from DNA to RNA to proteins. It covers DNA replication, transcription, translation, and how mutations can occur during these processes. DNA replication is semi-conservative and produces two identical DNA molecules from one original. Transcription produces mRNA from DNA, and translation uses mRNA to produce proteins according to the genetic code. Mutations can occur during replication, transcription or translation and result in changes to the amino acid sequence or reading frame of proteins.
The document describes the central dogma of molecular biology, which is the flow of genetic information from DNA to RNA to proteins. It covers DNA replication, transcription, translation, and how mutations can occur during these processes. DNA replication is semi-conservative and produces two identical DNA molecules from one original. Transcription produces mRNA from DNA, and translation uses mRNA to produce proteins according to the genetic code. Mutations can occur during replication, transcription or translation and result in changes to the amino acid sequence or reading frame of proteins.
The document describes the central dogma of molecular biology, which is the flow of genetic information from DNA to RNA to proteins. It covers DNA replication, transcription, translation, and how mutations can occur during these processes. DNA replication is semi-conservative and produces two identical DNA molecules from one original. Transcription produces mRNA from DNA, and translation uses mRNA to produce proteins according to the genetic code. Mutations can occur during replication, transcription or translation and result in changes to the amino acid sequence or reading frame of proteins.
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. It involves three main steps: replication, transcription, and translation. Replication copies DNA, transcription creates mRNA from DNA, and translation uses mRNA to produce proteins. The central dogma states that genetic information flows from DNA to RNA to protein. Mutations can occur and change the nucleotide sequence, potentially altering the amino acid sequence of the resulting protein.
DNA is made up of nucleotides containing nitrogen bases, sugars and phosphates. The bases on two DNA strands bond together through complementary base pairing between adenine and thymine, and cytosine and guanine. DNA replicates semi-conservatively through initiation, elongation, and termination steps. RNA carries instructions from DNA for protein production. Transcription involves RNA polymerase making mRNA from DNA. Translation uses mRNA, tRNAs, and ribosomes to assemble amino acids into proteins according to the genetic code of three-base codons. Mutations in DNA can alter codons and cause changes in protein sequences.
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A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
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Assessment and Planning in Educational technology.pptxKavitha Krishnan
In an education system, it is understood that assessment is only for the students, but on the other hand, the Assessment of teachers is also an important aspect of the education system that ensures teachers are providing high-quality instruction to students. The assessment process can be used to provide feedback and support for professional development, to inform decisions about teacher retention or promotion, or to evaluate teacher effectiveness for accountability purposes.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
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Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
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A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
The simplified electron and muon model, Oscillating Spacetime: The Foundation...RitikBhardwaj56
Discover the Simplified Electron and Muon Model: A New Wave-Based Approach to Understanding Particles delves into a groundbreaking theory that presents electrons and muons as rotating soliton waves within oscillating spacetime. Geared towards students, researchers, and science buffs, this book breaks down complex ideas into simple explanations. It covers topics such as electron waves, temporal dynamics, and the implications of this model on particle physics. With clear illustrations and easy-to-follow explanations, readers will gain a new outlook on the universe's fundamental nature.
3. 12.1 What Is the Evidence that Genes Code for Proteins? The gene-enzyme relationship has been revised to the one-gene, one-polypeptide relationship . Example: In hemoglobin, each polypeptide chain is specified by a separate gene. Other genes code for RNA that is not translated to polypeptides; some genes are involved in controlling other genes.
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6. 12.2 How Does Information Flow from Genes to Proteins? RNA can pair (hybridize) with a single strand of DNA, except that adenine pairs with uracil instead of thymine . Single-strand RNA can fold into complex shapes by internal base Pairing. (i.e. tRNA
7. Figure 12.2 The Central Dogma The central dogma of molecular biology: information flows in one direction when genes are expressed (Francis Crick). CENTRAL DOGMA: reverse transcriptase - HIV
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9. 12.2 How Does Information Flow from Genes to Proteins? Transcription : 1. Messenger hypothesis — messenger RNA ( mRNA ) forms as a complementary copy of DNA and carries information to the cytoplasm. from the nucleus to the cytosol - from ATGC to AUGC
10. Figure 12.3 From Gene to Protein Synthesis of DNA from RNA is reverse transcription . Viruses that do this are retroviruses .
11. 12.2 How Does Information Flow from Genes to Proteins? 2. Adapter hypothesis —an adapter molecule that can bind amino acids , and recognize a nucleotide sequence— transfer RNA ( tRNA ). Translation: tRNA molecules carrying amino acids line up on mRNA in proper sequence for the polypeptide chain AUGC to amino acid!
12. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? Within each gene, only one strand of DNA is transcribed—the template strand . Transcription produces mRNA; the same process is used to produce tRNA and rRNA . https://eapbiofield.wikispaces.com/Transcription+and+Translation+KW?f=print
13. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? RNA polymerases catalyze synthesis of RNA. RNA polymerases are processive — a single enzyme-template binding results in polymerization of hundreds of RNA bases.
14. Figure 12.4 RNA Polymerase What are the bonds called that form between ribose bases?
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16. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? Initiation requires a promoter —a special sequence of DNA. RNA polymerase binds to the promoter. Promoter tells RNA polymerase where to start, which direction to go in, and which strand of DNA to transcribe. Part of each promoter is the initiation site .
18. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? Elongation : RNA polymerase unwinds DNA about 10 base pairs at a time; reads template in 3' to 5' direction. The RNA transcript is antiparallel to the DNA template strand. RNA polymerases do not proofread and correct mistakes.
20. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? Termination : specified by a specific DNA base sequence. Mechanisms of termination are complex and varied. Eukaryotes—first product is a pre-mRNA that is longer than the final mRNA and must undergo processing.
22. mRNA Splicing The entire gene is transcripted into a message. Some of the message is Junk (introns) and is removed before exiting the nucleus. A spliceosome is a complex of specialized RNA and protein that removes introns from a pre-mRNA This process is generally referred to as splicing. Introns typically have a “GU” nucleotide sequence at the 5' end splice site, and an AG at the 3' end splice site.
23. Alternative splicing is a source of genetic diversity in eukaryotes. Splicing has been used to account for the relatively small number of genes in the human genome. Old estimates were for 100,000 genes but due to the Human Genome Project the figure is now roughly 20,000 genes. One particular Drosophila gene (DSCAM) can be alternatively spliced into 38,000 different mRNAs. http://vcell.ndsu.edu/animations/mrnasplicing/movie.htm
24. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? The genetic code : specifies which amino acids will be used to build a protein Codon : a sequence of three bases. Each codon specifies a particular amino acid. Start codon : AUG—initiation signal for translation – Always!! ( well some exceptions…) Stop codons : stops translation and polypeptide is released
26. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? For most amino acids, there is more than one codon; the genetic code is redundant . But not ambiguous —each codon specifies only one amino acid.
27. 12.3 How Is the Information Content in DNA Transcribed to Produce RNA? The genetic code is nearly universal : the codons that specify amino acids are the same in all organisms. Exceptions: within mitochondria and chloroplasts, and in one group of protists.
30. 12.4 How Is RNA Translated into Proteins? The conformation (three-dimensional shape) of tRNA results from base pairing (H bonds) within the molecule. 3' end is the amino acid attachment site— binds covalently. Always CCA. Anticodon : site of base pairing with mRNA. Unique for each species of tRNA.
31. 12.4 How Is RNA Translated into Proteins? Example: DNA codon for arginine: 3'-GCC-5' Complementary mRNA : 3'-CGG-5' Anticodon on the tRNA : 3'-GCC-5' This tRNA is charged with arginine. TAC - ___ ____ ____ - TAC
32. 12.4 How Is RNA Translated into Proteins? Wobble : specificity for the base at the 3' end of the codon is not always observed. Example: codons for alanine—GCA, GCC, and GCU—are recognized by the same tRNA.
33. 12.4 How Is RNA Translated into Proteins? Ribosome : the workbench—holds mRNA and tRNA in the correct positions to allow assembly of polypeptide chain. Ribosomes are not specific, they can make any type of protein.
34. Prokaryotes Small Subunit 30s Large subunit 50s 16s 5s 21 proteins 23s 34 proteins Eukaryotes: Small 40S Large 60S 5S 18S 28S 33 proteins 5.8S 49 proteins **The numbers are not additive – based on centrifugation rates
35. 12.4 How Is RNA Translated into Proteins? Subunits are held together by ionic and hydrophobic forces (not covalent bonds). When not active in translation, the subunits exist separately.
38. 12.4 How Is RNA Translated into Proteins? Hydrogen bonds form between the anticodon of tRNA and the codon of mRNA. Small subunit rRNA validates the match—if hydrogen bonds have not formed between all three base pairs, it must be an incorrect match, and the tRNA is rejected. quality control
39. 12.4 How Is RNA Translated into Proteins? Initiation : An initiation complex forms—charged tRNA, small subunit, both bound to mRNA. Essay worthy! Recount process in paragraph form. Diagrams a bonus!
40. Figure 12.11 The Initiation of Translation (Part 2) STEP 1 Step 2 http://www.biostudio.com/demo_freeman_protein_synthesis.htm
41. 12.4 How Is RNA Translated into Proteins? Start codon is AUG; first amino acid is always methionine, which may be removed after translation. The large subunit joins the complex, the charged tRNA is now in the P site of the large subunit.
42. 12.4 How Is RNA Translated into Proteins? Elongation : the second charged tRNA enters the A site. Large subunit catalyzes two reactions: 1. Breaks bond between tRNA in P site and its amino acid. 2. Peptide bond forms between that amino acid and the amino acid on tRNA in the A site.
45. 12.4 How Is RNA Translated into Proteins? Termination : translation ends when a stop codon enters the A site. Stop codon binds a protein release factor —allows hydrolysis of bond between polypeptide chain and tRNA on the P site. Polypeptide chain—C terminus is the last amino acid added.
51. 12.4 How Is RNA Translated into Proteins? Several ribosomes can work together to translate the same mRNA, producing multiple copies of the polypeptide. A strand of mRNA with associated ribosomes is called a polyribosome or polysome .
54. 12.5 What Happens to Polypeptides after Translation? 1. Polypeptide folds as it emerges from the ribosome. 2. The amino acid sequence determines the pattern of folding.
57. 2. Polyadenylation is the synthesis of a poly(A) tail, a stretch of adenines at the end of the mRNA molecule. At the end of transcription the last 3’ bit of the newly made RNA is cleaved off by a set aof enzymes. The enzymes then synthesize the poly(A) tail at the RNA's 3' end. The poly(A) tail is important for the nuclear export, translation and stability of mRNA. The tail is shortened over time and when it is short enough, the mRNA is degraded. In a few cell types, mRNAs with short poly(A) tails are stored for later activation Stabilizing the message
60. Figure 12.16 A Signal Sequence Moves a Polypeptide into the ER (Part 1)
61. Figure 12.16 A Signal Sequence Moves a Polypeptide into the ER (Part 2) Folding chaperones (proteins) in RER fold proteins appropriately. Mis-folding diseases: Altzheimer’s Creutzfeld–Jakob disease (CJD) (prion disease) P53 – cancer from misfolded “watchdog”
62. 12.5 What Happens to Polypeptides after Translation? 4. Glycosylation : addition of sugars to form glycoproteins Sugars may be added in the Golgi apparatus—the resulting glycoproteins end up in the plasma membrane, lysosomes, or vacuoles. Diseases: incorrect addition of sugars to specific amino acids – shows in infancy-almost always involves nervous system development.
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64. 12.5 What Happens to Polypeptides after Translation? Protein modifications: 5. Proteolysis : cutting the polypeptide chain by proteases . Degradation of protein message. 6. Phosphorylation : addition of phosphate groups by kinases. Charged phosphate groups change the conformation. Generally makes protein into enzymes!
67. 12.6 What Are Mutations? Somatic mutations occur in somatic (body) cells. Mutation is passed to daughter cells, but not to sexually produced offspring. Germ line mutations occur in cells that produce gametes. Can be passed to next generation.
68. 12.6 What Are Mutations? Conditional mutants : express phenotype only under restrictive conditions. Example: the allele may code for an enzyme that is unstable at certain temperatures.
69. 12.6 What Are Mutations? All mutations are alterations of the nucleotide sequence. Point mutations : change in a single base pair—loss, gain, or substitution of a base. Chromosomal mutations : change in segments of DNA—loss, duplication, or rearrangement.
70. 12.6 What Are Mutations? Point mutations can result from replication and proofreading errors, or from environmental mutagens. Silent mutations have no effect on the protein because of the redundancy of the genetic code. Silent mutations result in genetic diversity not expressed as phenotype differences.
72. 12.6 What Are Mutations? Missense mutations : base substitution results in amino acid substitution.
73. 12.6 What Are Mutations? Sickle allele for human â-globin is a missense mutation. Sickle allele differs from normal by only one base—the polypeptide differs by only one amino acid. Individuals that are homozygous have sickle-cell disease.
75. 12.6 What Are Mutations? Nonsense mutations : base substitution results in a stop codon.
76. 12.6 What Are Mutations? Frame-shift mutations : single bases inserted or deleted—usually leads to nonfunctional proteins.
77. 12.6 What Are Mutations? Chromosomal mutations: Deletions —severe consequences unless it affects unnecessary genes or is masked by normal alleles. Duplications —if homologous chromosomes break in different places and recombine with the wrong partners.
79. 12.6 What Are Mutations? Chromosomal mutations: Inversions —breaking and rejoining, but segment is “flipped.” Translocations —segment of DNA breaks off and is inserted into another chromosome. Can cause duplications and deletions. Meiosis can be prevented if chromosome pairing is impossible.
83. 12.6 What Are Mutations? Induced mutation —due to an outside agent, a mutagen. Chemicals can alter bases (e.g., nitrous acid can cause deamination). Some chemicals add other groups to bases (e.g., benzpyrene adds a group to guanine and prevents base pairing). DNA polymerase will then add any base there.
84. 12.6 What Are Mutations? Ionizing radiation such as X-rays create free radicals—highly reactive—can change bases, break sugar phosphate bonds. UV radiation is absorbed by thymine, causing it to form covalent bonds with adjacent nucleotides—disrupts DNA replication.
87. 12.6 What Are Mutations? Mutation provides the raw material for evolution in the form of genetic diversity. Mutations can harm the organism, or be neutral. Occasionally, a mutation can improve an organism’s adaptation to its environment, or become favorable as conditions change.
88. 12.6 What Are Mutations? Complex organisms tend to have more genes than simple organisms. If whole genes are duplicated, the new genes would be surplus genetic information. Extra copies could lead to the production of new proteins. New genes can also arise from transposable elements (see Chapters 13 and 14).