DNA, chromosomes and genomes Notes based on molecular biology of the cell. Biology Elite: biologyelite.weebly.com, please use together with the presentation
How cells read the genome from DNA to protein NotesYi Fan Chen
The document summarizes the process of transcription and translation in cells. It describes:
1) Transcription of DNA to RNA which is catalyzed by RNA polymerase and involves the formation of RNA through the addition of ribonucleotides.
2) Processing of eukaryotic pre-mRNA which involves capping, splicing, and polyadenylation to form mature mRNA.
3) Translation of mRNA to protein which occurs on ribosomes and involves tRNAs carrying amino acids that are linked together through peptide bond formation catalyzed by the ribosome. Accuracy is ensured by induced fit binding and kinetic proofreading.
DNA replication, repair and recombination NotesYi Fan Chen
DNA, replication, repair and recombination Notes based on Molecular biology of the cell. Biology Elite: biologyelite.weebly.com, please use together with the presentation
Mutations arise from errors in DNA replication or damage from mutagens. They can be point mutations involving a single nucleotide change or larger mutations like deletions, duplications, or inversions. Cells have DNA repair enzymes that minimize mutations by correcting errors during and after replication. However, some mutations evade repair and become permanent if replicated into new daughter DNA. Trinucleotide repeat expansions can cause neurological diseases if the repeats grow too long during replication due to slippage at repeated sequences. Cells deal with DNA damage through bypass, repair, or removal and replacement of damaged sections.
DNA repair is essential to prevent damage from impairing organism survival and potentially causing cancer. The main types of DNA repair are mismatch repair, direct repair, base-excision repair, and nucleotide-excision repair. Mismatch repair in E. coli involves the MutS, MutH, and MutL proteins detecting mismatches that are then repaired. Direct repair directly changes altered bases back to their original structures using enzymes like MGMT. Base-excision repair removes small base lesions using DNA glycosylases and polymerases. Nucleotide-excision repair removes bulky UV-induced DNA adducts by cleaving and removing the damaged strand.
1. DNA replication is semi-conservative. Helicase unwinds the DNA double helix, DNA polymerase links nucleotides to form new strands using the existing strands as templates.
2. Transcription creates mRNA from DNA templates using RNA polymerase.
3. Translation uses the genetic code to synthesize polypeptides from mRNA. tRNAs with anticodons complementary to mRNA codons carry amino acids which are linked by the ribosome.
The document discusses the genetic code, which is a set of rules that specifies how sequences of nucleotides in DNA and RNA are translated into proteins. It notes that the genetic code is universal, uses triplets of nucleotides (codons), and has some level of degeneracy whereby more than one codon can code for an amino acid. This redundancy is explained by Crick's wobble hypothesis regarding base pairing at the third position of codons and anticodons.
This document summarizes DNA replication. It describes the key requirements for replication like dNTPs, template DNA, primers, and magnesium ions. It explains that replication is semi-conservative, with each parental strand serving as a template for the daughter strands. It discusses the different models of replication and evidence from Meselson and Stahl's experiment supporting the semi-conservative model. It also provides details about replication proteins, the replication fork, and differences between prokaryotic and eukaryotic replication.
How cells read the genome from DNA to protein NotesYi Fan Chen
The document summarizes the process of transcription and translation in cells. It describes:
1) Transcription of DNA to RNA which is catalyzed by RNA polymerase and involves the formation of RNA through the addition of ribonucleotides.
2) Processing of eukaryotic pre-mRNA which involves capping, splicing, and polyadenylation to form mature mRNA.
3) Translation of mRNA to protein which occurs on ribosomes and involves tRNAs carrying amino acids that are linked together through peptide bond formation catalyzed by the ribosome. Accuracy is ensured by induced fit binding and kinetic proofreading.
DNA replication, repair and recombination NotesYi Fan Chen
DNA, replication, repair and recombination Notes based on Molecular biology of the cell. Biology Elite: biologyelite.weebly.com, please use together with the presentation
Mutations arise from errors in DNA replication or damage from mutagens. They can be point mutations involving a single nucleotide change or larger mutations like deletions, duplications, or inversions. Cells have DNA repair enzymes that minimize mutations by correcting errors during and after replication. However, some mutations evade repair and become permanent if replicated into new daughter DNA. Trinucleotide repeat expansions can cause neurological diseases if the repeats grow too long during replication due to slippage at repeated sequences. Cells deal with DNA damage through bypass, repair, or removal and replacement of damaged sections.
DNA repair is essential to prevent damage from impairing organism survival and potentially causing cancer. The main types of DNA repair are mismatch repair, direct repair, base-excision repair, and nucleotide-excision repair. Mismatch repair in E. coli involves the MutS, MutH, and MutL proteins detecting mismatches that are then repaired. Direct repair directly changes altered bases back to their original structures using enzymes like MGMT. Base-excision repair removes small base lesions using DNA glycosylases and polymerases. Nucleotide-excision repair removes bulky UV-induced DNA adducts by cleaving and removing the damaged strand.
1. DNA replication is semi-conservative. Helicase unwinds the DNA double helix, DNA polymerase links nucleotides to form new strands using the existing strands as templates.
2. Transcription creates mRNA from DNA templates using RNA polymerase.
3. Translation uses the genetic code to synthesize polypeptides from mRNA. tRNAs with anticodons complementary to mRNA codons carry amino acids which are linked by the ribosome.
The document discusses the genetic code, which is a set of rules that specifies how sequences of nucleotides in DNA and RNA are translated into proteins. It notes that the genetic code is universal, uses triplets of nucleotides (codons), and has some level of degeneracy whereby more than one codon can code for an amino acid. This redundancy is explained by Crick's wobble hypothesis regarding base pairing at the third position of codons and anticodons.
This document summarizes DNA replication. It describes the key requirements for replication like dNTPs, template DNA, primers, and magnesium ions. It explains that replication is semi-conservative, with each parental strand serving as a template for the daughter strands. It discusses the different models of replication and evidence from Meselson and Stahl's experiment supporting the semi-conservative model. It also provides details about replication proteins, the replication fork, and differences between prokaryotic and eukaryotic replication.
POST TRANSCRIPTIONAL MODIFICATIONS IN EUKARYOTESSidra Shaffique
1) Eukaryotic mRNAs undergo post-transcriptional processing in the cell nucleus, including addition of a 5' cap and 3' polyadenylated tail.
2) The 5' cap consists of a 7-methylguanosine residue joined to the initial nucleotide via a 5'-5' triphosphate bridge, and is added co-transcriptionally.
3) Mature mRNAs also contain a poly(A) tail of around 250 nucleotides added by poly(A) polymerase to the 3' end after cleavage of the primary transcript.
regulation of gene expression in eukaryotes is a complex mechanism involved many factors. out of many levels of regulations, chromosomal and transcription level of regulation are discussed in this slides.
This document summarizes translation mechanisms in prokaryotic and eukaryotic systems. It discusses that translation is the process of protein synthesis from mRNA, involving ribosomes, tRNAs, and enzymes. The three main steps of translation - initiation, elongation, and termination - are described for both prokaryotic and eukaryotic systems. Key differences between the two systems are the use of Shine-Dalgarno sequences and initiation factors in prokaryotes versus Kozak sequences and more complex initiation factor involvement in eukaryotes. Termination and ribosome recycling mechanisms are also compared between prokaryotes and eukaryotes.
Epigenetics is the study of mechanisms that control which genes are switched on or off. It involves epigenetic mechanisms like methylation and histone modification that manipulate the genome without changing the DNA sequence. Experiments show that exposures like chemicals, smoking, diet, and stress during pregnancy can cause epigenetic changes that affect gene expression and traits in subsequent generations. A study in Sweden found that poor harvests and malnutrition during pregnancy were associated with higher risk of cardiovascular disease in offspring, and periods of feast after famine extended this risk to grandchildren through epigenetic inheritance. Understanding epigenetics is important for studying evolution and treating diseases like cancer, genetic disorders, immunity and neuropsychiatric conditions.
Split genes contain both coding (exon) and non-coding (intron) regions. During mRNA splicing, introns are removed from pre-mRNA and exons are joined together to form mature mRNA. This process is catalyzed by the spliceosome, a complex of five small nuclear RNAs and numerous proteins. The spliceosome facilitates two transesterification reactions which remove the intron and ligate the exons, allowing gene sequences to code for multiple proteins through alternative splicing. Splicing increases gene and protein diversity in the cell.
This document discusses the organization of chromatin and DNA packaging in the cell nucleus. It describes four main levels of chromatin organization: 1) DNA wraps around histone proteins to form nucleosomes, the basic unit of chromatin, 2) Nucleosomes further organize into 30nm fibers, 3) The 30nm fibers then organize into looped domains, and 4) During cell division, the loops compact into mitotic chromosomes. Nucleosomes consist of about 150 base pairs of DNA wrapped around an octamer of core histone proteins, and act to tightly package DNA inside the nucleus.
Baculovirus mediated gene expression and its veterinary applications discusses the baculovirus expression vector system (BEVS) for producing recombinant proteins. Key points include:
1. Baculoviruses infect insect cells and can be engineered to express foreign genes controlled by strong viral promoters.
2. The BEVS involves cloning a gene of interest into a baculovirus shuttle vector, transposing it into a bacmid, and transfecting the recombinant bacmid into insect cells to produce recombinant baculovirus and express the foreign protein.
3. The BEVS offers advantages like post-translational modifications, but applications are limited to proteins that do not require mammalian-
RNA-directed DNA methylation (RdDM) is an epigenetic pathway in plants and fungi where small RNAs direct DNA methylation and transcriptional gene silencing. The process involves RNA polymerase IV transcribing RNA from the locus to be silenced. This RNA is then copied to double stranded RNA by RNA-dependent RNA polymerase 2 and processed into 24 nucleotide small interfering RNAs by Dicer-like 3. Argonaute 4 incorporates these siRNAs and guides DNA methyltransferases like Domains Rearranged Methyltransferase 2 to introduce methyl groups at cytosines in DNA, leading to transcriptional gene silencing of the locus. RdDM is an important genome defense mechanism in plants against viruses.
This document provides information about transcription in prokaryotes. It defines transcription as the synthesis of RNA using single-stranded DNA as a template. It describes the basic requirements for transcription including the template, enzyme, regulatory proteins, ribonucleoside triphosphates, and energy. It then explains the three main steps of transcription - initiation, elongation, and termination - and provides details about each step. The document also discusses transcription regulation and inhibitors like rifampicin and actinomycin D.
There are two types of chaperone proteins that help other proteins fold: those that assist during folding and those that assist after folding. Heat shock proteins are an important type of chaperone that assists protein folding. Chaperone proteins help ensure proteins fold into their proper 3D shapes.
This document discusses microtubules and their role in cell movement. It describes how vincristine and vinblastine inhibit microtubule polymerization and cell division in rapidly dividing cells. It also discusses dynamic instability in microtubule growth and shrinkage cycles. The document outlines how microtubules extend from the centrosome in animal cells and form the mitotic spindle. It describes the structure of the centrosome and centrioles, and how gamma-tubulin nucleates microtubule assembly. Finally, it briefly summarizes microtubule organization in cells and their role in processes like cargo transport, cilia/flagella movement, and chromosome movement during mitosis.
1. Viral genomes contain DNA or RNA and are packaged into capsids through assembly processes. Bacterial chromosomes contain genes and other sequences compacted by looping and supercoiling.
2. Eukaryotic chromosomes vary greatly in size and contain genes and other sequences. Their DNA must be highly compacted to fit in the nucleus.
3. Eukaryotic DNA wraps around histone proteins to form nucleosomes, which further compact to form chromatin fibers and loop domains anchored to the nuclear matrix. Additional compaction occurs during cell division through condensin and cohesin proteins.
DNA, RNA, and proteins are the basic components of molecular biology. DNA stores genetic information and is replicated for cell division, while RNA acts as an intermediary to help synthesize proteins according to the genetic code. Molecular biologists study the interactions between these molecules to understand how life processes like DNA replication, transcription, and translation work at the cellular level.
The document summarizes key concepts about gene expression and analysis. It describes the central dogma of biology where DNA is transcribed into RNA which is then translated into protein. Gene structure is explained, noting that eukaryotic genes contain introns and exons. The roles of DNA, RNA and proteins in gene expression are outlined. The processes of transcription, including initiation, elongation and termination are summarized. Post-transcriptional processing of RNA including capping, splicing and polyadenylation is covered. Translation including initiation, elongation and termination is also summarized concisely. Control of gene expression occurs at transcriptional, post-transcriptional, translational and post-translational levels.
Homologous recombination is a process where DNA breaks and recombines to produce new combinations of genes. It occurs during meiosis through the pairing of homologous chromosomes between maternal and paternal copies. This leads to genetic diversity in offspring and crossing over, where segments are exchanged between chromosomes. Defects in homologous recombination can cause nondisjunction and diseases like cancer due to inefficient DNA repair.
Cot curve dispersed repeated DNA or interspersed repeated DNA tandem repeated DNA Long interspersed repeat sequences (LINEs) Short interspersed nuclear elements (SINEs) satellite, minisatellite and microsatellite DNA Variable Number Tandem Repeat (or VNTR)
DNA is the genetic material found in the nucleus of eukaryotic cells and in the chromosomes of prokaryotes. It exists in several forms, including linear chromosomes in eukaryotes and circular chromosomes in prokaryotes and organelles. DNA is made up of a double helix structure stabilized by hydrogen bonding between complementary nucleotide base pairs. The structure of DNA allows it to efficiently store and transmit genetic information.
Genetic recombination involves the exchange of genetic material between chromosomes or DNA molecules. It occurs through two main types - homologous recombination, which exchanges DNA between similar sequences, and non-homologous recombination between dissimilar sequences. Recombination is important for genetic diversity, DNA repair, and proper chromosome segregation during cell division. It can happen during both mitosis and meiosis, but only meiotic recombination shuffles genes from parents to offspring. There are also different mechanisms of recombination, including site-specific, transposition, and various DNA repair pathways that facilitate genetic exchange.
This document describes the process of DNA replication in eukaryotes. It occurs in S phase of the cell cycle and involves three main stages: initiation, formation of the initiation complex, and elongation. Initiation requires the assembly of pre-replication complexes containing ORC, Cdc6, Cdt1 and MCM proteins. In S phase, Cdc45 and GINS are recruited to form the initiation complex. Elongation proceeds bidirectionally from replication forks, with leading strand synthesis continuous and lagging strand discontinuous via Okazaki fragments. Replication terminates at telomeres.
The document summarizes eukaryotic chromosomal organization. It discusses that eukaryotic chromosomes contain linear DNA molecules that are highly compacted through wrapping around histone proteins. This forms chromatin, which exists in two forms - euchromatin that is loosely packed and facilitates transcription, and heterochromatin that is tightly packed and prevents transcription. The document outlines the various levels of compaction from DNA to nucleosomes to chromatin fibers and chromosomes, and describes the roles and modifications of histone and non-histone proteins in chromatin organization and gene regulation.
1. The document discusses genome size, structure of eukaryotic chromosomes, and chromatin structure. It describes how DNA is packaged at different levels within the cell, from nucleosomes to chromatin fibers to condensed mitotic chromosomes.
2. Key points include that genome size varies between organisms but is not correlated with complexity, and that eukaryotic DNA contains more non-coding regions like introns, resulting in lower gene density. DNA is packaged into nucleosomes containing histones then further condensed through different levels to form metaphase chromosomes.
3. Chromatin exists in two main forms, loosely packed euchromatin and tightly packed heterochromatin, which can be facultative and condense during certain phases or in
POST TRANSCRIPTIONAL MODIFICATIONS IN EUKARYOTESSidra Shaffique
1) Eukaryotic mRNAs undergo post-transcriptional processing in the cell nucleus, including addition of a 5' cap and 3' polyadenylated tail.
2) The 5' cap consists of a 7-methylguanosine residue joined to the initial nucleotide via a 5'-5' triphosphate bridge, and is added co-transcriptionally.
3) Mature mRNAs also contain a poly(A) tail of around 250 nucleotides added by poly(A) polymerase to the 3' end after cleavage of the primary transcript.
regulation of gene expression in eukaryotes is a complex mechanism involved many factors. out of many levels of regulations, chromosomal and transcription level of regulation are discussed in this slides.
This document summarizes translation mechanisms in prokaryotic and eukaryotic systems. It discusses that translation is the process of protein synthesis from mRNA, involving ribosomes, tRNAs, and enzymes. The three main steps of translation - initiation, elongation, and termination - are described for both prokaryotic and eukaryotic systems. Key differences between the two systems are the use of Shine-Dalgarno sequences and initiation factors in prokaryotes versus Kozak sequences and more complex initiation factor involvement in eukaryotes. Termination and ribosome recycling mechanisms are also compared between prokaryotes and eukaryotes.
Epigenetics is the study of mechanisms that control which genes are switched on or off. It involves epigenetic mechanisms like methylation and histone modification that manipulate the genome without changing the DNA sequence. Experiments show that exposures like chemicals, smoking, diet, and stress during pregnancy can cause epigenetic changes that affect gene expression and traits in subsequent generations. A study in Sweden found that poor harvests and malnutrition during pregnancy were associated with higher risk of cardiovascular disease in offspring, and periods of feast after famine extended this risk to grandchildren through epigenetic inheritance. Understanding epigenetics is important for studying evolution and treating diseases like cancer, genetic disorders, immunity and neuropsychiatric conditions.
Split genes contain both coding (exon) and non-coding (intron) regions. During mRNA splicing, introns are removed from pre-mRNA and exons are joined together to form mature mRNA. This process is catalyzed by the spliceosome, a complex of five small nuclear RNAs and numerous proteins. The spliceosome facilitates two transesterification reactions which remove the intron and ligate the exons, allowing gene sequences to code for multiple proteins through alternative splicing. Splicing increases gene and protein diversity in the cell.
This document discusses the organization of chromatin and DNA packaging in the cell nucleus. It describes four main levels of chromatin organization: 1) DNA wraps around histone proteins to form nucleosomes, the basic unit of chromatin, 2) Nucleosomes further organize into 30nm fibers, 3) The 30nm fibers then organize into looped domains, and 4) During cell division, the loops compact into mitotic chromosomes. Nucleosomes consist of about 150 base pairs of DNA wrapped around an octamer of core histone proteins, and act to tightly package DNA inside the nucleus.
Baculovirus mediated gene expression and its veterinary applications discusses the baculovirus expression vector system (BEVS) for producing recombinant proteins. Key points include:
1. Baculoviruses infect insect cells and can be engineered to express foreign genes controlled by strong viral promoters.
2. The BEVS involves cloning a gene of interest into a baculovirus shuttle vector, transposing it into a bacmid, and transfecting the recombinant bacmid into insect cells to produce recombinant baculovirus and express the foreign protein.
3. The BEVS offers advantages like post-translational modifications, but applications are limited to proteins that do not require mammalian-
RNA-directed DNA methylation (RdDM) is an epigenetic pathway in plants and fungi where small RNAs direct DNA methylation and transcriptional gene silencing. The process involves RNA polymerase IV transcribing RNA from the locus to be silenced. This RNA is then copied to double stranded RNA by RNA-dependent RNA polymerase 2 and processed into 24 nucleotide small interfering RNAs by Dicer-like 3. Argonaute 4 incorporates these siRNAs and guides DNA methyltransferases like Domains Rearranged Methyltransferase 2 to introduce methyl groups at cytosines in DNA, leading to transcriptional gene silencing of the locus. RdDM is an important genome defense mechanism in plants against viruses.
This document provides information about transcription in prokaryotes. It defines transcription as the synthesis of RNA using single-stranded DNA as a template. It describes the basic requirements for transcription including the template, enzyme, regulatory proteins, ribonucleoside triphosphates, and energy. It then explains the three main steps of transcription - initiation, elongation, and termination - and provides details about each step. The document also discusses transcription regulation and inhibitors like rifampicin and actinomycin D.
There are two types of chaperone proteins that help other proteins fold: those that assist during folding and those that assist after folding. Heat shock proteins are an important type of chaperone that assists protein folding. Chaperone proteins help ensure proteins fold into their proper 3D shapes.
This document discusses microtubules and their role in cell movement. It describes how vincristine and vinblastine inhibit microtubule polymerization and cell division in rapidly dividing cells. It also discusses dynamic instability in microtubule growth and shrinkage cycles. The document outlines how microtubules extend from the centrosome in animal cells and form the mitotic spindle. It describes the structure of the centrosome and centrioles, and how gamma-tubulin nucleates microtubule assembly. Finally, it briefly summarizes microtubule organization in cells and their role in processes like cargo transport, cilia/flagella movement, and chromosome movement during mitosis.
1. Viral genomes contain DNA or RNA and are packaged into capsids through assembly processes. Bacterial chromosomes contain genes and other sequences compacted by looping and supercoiling.
2. Eukaryotic chromosomes vary greatly in size and contain genes and other sequences. Their DNA must be highly compacted to fit in the nucleus.
3. Eukaryotic DNA wraps around histone proteins to form nucleosomes, which further compact to form chromatin fibers and loop domains anchored to the nuclear matrix. Additional compaction occurs during cell division through condensin and cohesin proteins.
DNA, RNA, and proteins are the basic components of molecular biology. DNA stores genetic information and is replicated for cell division, while RNA acts as an intermediary to help synthesize proteins according to the genetic code. Molecular biologists study the interactions between these molecules to understand how life processes like DNA replication, transcription, and translation work at the cellular level.
The document summarizes key concepts about gene expression and analysis. It describes the central dogma of biology where DNA is transcribed into RNA which is then translated into protein. Gene structure is explained, noting that eukaryotic genes contain introns and exons. The roles of DNA, RNA and proteins in gene expression are outlined. The processes of transcription, including initiation, elongation and termination are summarized. Post-transcriptional processing of RNA including capping, splicing and polyadenylation is covered. Translation including initiation, elongation and termination is also summarized concisely. Control of gene expression occurs at transcriptional, post-transcriptional, translational and post-translational levels.
Homologous recombination is a process where DNA breaks and recombines to produce new combinations of genes. It occurs during meiosis through the pairing of homologous chromosomes between maternal and paternal copies. This leads to genetic diversity in offspring and crossing over, where segments are exchanged between chromosomes. Defects in homologous recombination can cause nondisjunction and diseases like cancer due to inefficient DNA repair.
Cot curve dispersed repeated DNA or interspersed repeated DNA tandem repeated DNA Long interspersed repeat sequences (LINEs) Short interspersed nuclear elements (SINEs) satellite, minisatellite and microsatellite DNA Variable Number Tandem Repeat (or VNTR)
DNA is the genetic material found in the nucleus of eukaryotic cells and in the chromosomes of prokaryotes. It exists in several forms, including linear chromosomes in eukaryotes and circular chromosomes in prokaryotes and organelles. DNA is made up of a double helix structure stabilized by hydrogen bonding between complementary nucleotide base pairs. The structure of DNA allows it to efficiently store and transmit genetic information.
Genetic recombination involves the exchange of genetic material between chromosomes or DNA molecules. It occurs through two main types - homologous recombination, which exchanges DNA between similar sequences, and non-homologous recombination between dissimilar sequences. Recombination is important for genetic diversity, DNA repair, and proper chromosome segregation during cell division. It can happen during both mitosis and meiosis, but only meiotic recombination shuffles genes from parents to offspring. There are also different mechanisms of recombination, including site-specific, transposition, and various DNA repair pathways that facilitate genetic exchange.
This document describes the process of DNA replication in eukaryotes. It occurs in S phase of the cell cycle and involves three main stages: initiation, formation of the initiation complex, and elongation. Initiation requires the assembly of pre-replication complexes containing ORC, Cdc6, Cdt1 and MCM proteins. In S phase, Cdc45 and GINS are recruited to form the initiation complex. Elongation proceeds bidirectionally from replication forks, with leading strand synthesis continuous and lagging strand discontinuous via Okazaki fragments. Replication terminates at telomeres.
The document summarizes eukaryotic chromosomal organization. It discusses that eukaryotic chromosomes contain linear DNA molecules that are highly compacted through wrapping around histone proteins. This forms chromatin, which exists in two forms - euchromatin that is loosely packed and facilitates transcription, and heterochromatin that is tightly packed and prevents transcription. The document outlines the various levels of compaction from DNA to nucleosomes to chromatin fibers and chromosomes, and describes the roles and modifications of histone and non-histone proteins in chromatin organization and gene regulation.
1. The document discusses genome size, structure of eukaryotic chromosomes, and chromatin structure. It describes how DNA is packaged at different levels within the cell, from nucleosomes to chromatin fibers to condensed mitotic chromosomes.
2. Key points include that genome size varies between organisms but is not correlated with complexity, and that eukaryotic DNA contains more non-coding regions like introns, resulting in lower gene density. DNA is packaged into nucleosomes containing histones then further condensed through different levels to form metaphase chromosomes.
3. Chromatin exists in two main forms, loosely packed euchromatin and tightly packed heterochromatin, which can be facultative and condense during certain phases or in
The document summarizes the molecular organization of chromosomes in eukaryotic cells. It discusses that [I] chromatin is composed of DNA wound around histone proteins to form bead-like nucleosomes connected by "linker DNA". [II] Nucleosomes assemble into fibers that further coil to form condensed chromosomes. [III] Chromosomes also contain specialized regions like centromeres that aid in chromosome segregation during cell division and telomeres that protect chromosome ends.
The document discusses the structure and organization of DNA and chromosomes in prokaryotes and eukaryotes. It explains that in prokaryotes, DNA is located in the cytoplasm and not enclosed in a nucleus, while in eukaryotes DNA is packaged into chromosomes within the nucleus. The basic unit of chromatin in eukaryotes is the nucleosome, which involves DNA wound around an octamer of core histone proteins (H2A, H2B, H3, H4). This facilitates a high level of DNA compaction through hierarchical levels of organization involving histone modifications and DNA-binding proteins.
The document summarizes the organization of the human genome and genes. It discusses the general organization of the human genome including nuclear and mitochondrial genomes. It describes gene distribution and density in the nuclear genome. It provides details on the organization of different types of genes such as rRNA, mRNA, small nuclear RNA genes, overlapping genes, and multi-gene families. It also discusses various repetitive elements in the genome including SINEs, LINEs, microsatellites, and minisatellites. Finally, it covers topics like chromatin structure, histones, heterochromatin, euchromatin, and X-inactivation.
Histones are positively charged proteins that package DNA into nucleosomes, the basic units of chromatin. Nucleosomes consist of DNA wrapped around an octamer of core histone proteins (H3, H4, H2A, H2B), with additional wrapping facilitated by linker histone H1. Post-translational modifications to histones, such as methylation, acetylation, and phosphorylation, alter their charge and impact chromatin compaction. Tightly packed heterochromatin contains genes that are generally transcriptionally silent, while the looser euchromatin allows gene expression.
The document discusses several key topics related to DNA structure and function:
DNA replication ensures each cell has an exact copy of the DNA before cell division. Errors are constantly checked and repaired to maintain high fidelity. DNA is also rearranged through processes like recombination. The tightly regulated enzymes that perform these metabolic processes were demonstrated by the Meselson-Stahl experiment to replicate DNA using a semiconservative mechanism. DNA is organized through various levels of compaction into condensed chromosomes. This dynamic structure, along with features like centromeres and telomeres, helps regulate DNA accessibility and proper segregation during cell division.
The document discusses the organization and packaging of human DNA within chromosomes. It describes how DNA is wrapped around histone proteins to form nucleosomes, which further compact to form 30nm chromatin fibers. These fibers then loop and fold at increasing levels of organization, ultimately forming condensed metaphase chromosomes approximately 700nm wide that contain the entire human genome in a highly packaged form within cell nuclei.
The document summarizes yeast chromosome structure and function. It discusses how DNA is packaged into chromatin and nucleosomes in yeast. The yeast genome contains 16 chromosomes with centromeres and telomeres. Histones can be post-translationally modified through acetylation, deacetylation, and methylation, which impacts chromatin structure and gene expression. Centromeres, origins of replication, and telomeres are also described.
Chromatin Structure & Genome Organization by Shivendra Kumarshivendra kumar
1. The document discusses the structure of chromatin and chromosomes. It describes how DNA is packaged into nucleosomes, which are composed of histone proteins wrapped around DNA.
2. Nucleosomes further compact the DNA to form a 30nm fiber, which is then folded into loops and domains to achieve higher order compaction into chromosomes. This compaction allows the long DNA molecules to fit inside cells.
3. Chromatin structure influences gene expression, with tightly packed heterochromatin generally transcriptionally inactive and loosely packed euchromatin more active. Histone modifications also impact chromatin structure and gene expression.
Facts about DNA
Eukaryotic chromosomes
Chemical composition of eukaryotic chromosomes
Histones
Non-histone chromosomal protein
Scaffold proteins
Folded fibre model
Nucleosome model
H1 proteins
Histone modification
Chromatosome
Higher order of chromatin structure
Mechanism of DNA packaging
Conclusion
The document summarizes key aspects of chromosome structure and behavior during cell division. It describes how DNA is wrapped around histone proteins to form chromatin and nucleosomes. It explains that centromeres attach to spindle fibers and pull chromosomes during cell division, while telomeres are repetitive DNA sequences at chromosome ends. The document also outlines the differences between mitosis, which produces two identical daughter cells, and meiosis, which involves two cell divisions to generate four haploid gametes through homologous chromosome pairing and independent assortment.
Chromosomes are organized structures that package DNA and proteins in eukaryotic cells. Bacterial genetic material is concentrated in the nucleoid as a single circular DNA chromosome. Eukaryotic cells contain linear chromosomes housed within the nucleus. Chromosomes are made up of DNA, histone proteins, and non-histone proteins. They contain genes and regulatory elements and vary in structure between species.
The document discusses the organization and structure of the human genome. It notes that the genome contains DNA arranged into genes on chromosomes within the cell nucleus, as well as mitochondrial DNA containing 37 genes. The human genome consists of 24 chromosomes in the nucleus plus the mitochondrial genome. DNA is organized into nucleosomes and packaged into chromatin and chromosomes. Genes encode instructions to make proteins and are regulated differently between cell types.
This document discusses chromosome structure and organization with respect to nucleosomes. It begins by defining genetic material and describing its forms in prokaryotes and eukaryotes. It then discusses the components of chromatin, including histone and non-histone proteins. It describes how DNA wraps around histone proteins to form nucleosomes, and how nucleosomes further organize into higher-order structures like the 30nm fiber. The document concludes by explaining how condensin proteins facilitate chromosome condensation during cell division.
The document discusses chromatin structure and organization. It describes how DNA is packaged into nucleosomes, which consist of 146bp of DNA wrapped around an octamer of histone proteins (H2A, H2B, H3, H4). Nucleosomes interact with each other and linker histone H1 to form higher-order chromatin structures. Histone proteins play a key role in chromatin organization and undergo various post-translational modifications that influence chromatin structure and gene expression. The document also discusses histone variants and their different functions in chromatin.
Cytogenetics_ Chromosmes_Dr Jagadisha T V_PPT.pptxJagadishaTV
●To study the structure of chromosomes.
● To understand the concepts of linkage and crossing over.
● To understand structural and numerical chromosomal aberrations.
1. DNA carries genetic information that is stored in genes located on chromosomes within cells.
2. The structure of DNA was determined in 1953 by Watson and Crick to be a double helix with complementary nucleotide base pairing.
3. Genes contain the instructions to make proteins and RNA and are arranged linearly along chromosomes in eukaryotic cells.
DNA is highly compacted in cells through various levels of supercoiling and chromatin structure. At the most basic level, DNA wraps around histone proteins to form nucleosomes, introducing negative supercoiling. Nucleosomes are then packed into a beads-on-a-string structure and further compacted into the 30nm fiber. Additional folding compacts the DNA over 10,000-fold into the final chromosomes. The two main types of supercoiling that facilitate compaction are plectonemic and solenoidal, with solenoidal supercoiling allowing the greatest degree of compaction and found in chromatin.
Similar to DNA, chromosomes and genomes Notes (20)
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
"Learn about all the ways Walmart supports nonprofit organizations.
You will hear from Liz Willett, the Head of Nonprofits, and hear about what Walmart is doing to help nonprofits, including Walmart Business and Spark Good. Walmart Business+ is a new offer for nonprofits that offers discounts and also streamlines nonprofits order and expense tracking, saving time and money.
The webinar may also give some examples on how nonprofits can best leverage Walmart Business+.
The event will cover the following::
Walmart Business + (https://business.walmart.com/plus) is a new shopping experience for nonprofits, schools, and local business customers that connects an exclusive online shopping experience to stores. Benefits include free delivery and shipping, a 'Spend Analytics” feature, special discounts, deals and tax-exempt shopping.
Special TechSoup offer for a free 180 days membership, and up to $150 in discounts on eligible orders.
Spark Good (walmart.com/sparkgood) is a charitable platform that enables nonprofits to receive donations directly from customers and associates.
Answers about how you can do more with Walmart!"
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.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
1. Biology Elite biologyelite.weebly.com
Part II Chapter 4 DNA, Chromosomes and genomes
Base pairing:
• purines: adenine and guanine (heavier and longer, two rings)
• pyrimidines: thyme and cytosine (lighter and shorter, one ring)
• each base pairing is in similar width, holding the sugar backbones a constant distance
• two hydrogen bonds forming between A and T
• three hydrogen bonds forming between C and G
• Each turn of DNA contains 10 base pairs
Packaging of DNA:
• prevent form unmanageable tangle of DNA
• remain accessible for some section of DNA
• Chromosomes: a single, enormously long linear DNA molecule along with the proteins that fold
and pack the one DNA thread into a more compact structure
• each human cell (except gametes) contains two copies of each chromosome, one from mother
and one form father, called “homologous chromosomes (homologs)”
• nonhomologous chromosome pairs are sex chromosomes (Y-father, X-mother, XY-male, XX-
female)
• each human cell contains 46 chromosomes, 22 pairs of homologs and 1 pair of sex chromosome
• distinguish of chromosomes: DNA hybridisation (colour painting using fluorescent dyes); stain
them with dyes (showing patterns of bands)
• display of the 46 chromosomes at mitosis is called human karyotype
• abnormalities of chromosome can be detected by banding patterns or chromosome painting
• gene: a segment of DNA that contains the instructions for making a particular protein
Specialised nucleotide sequence:
• Replication origins: the location where the duplication of DNA begins
• Centromere: allow one copy of each duplicated and condensed chromosome to be pulled into
each daughter cells when a cell divide. Kinetochore (protein complex) forms at the centromere,
making the chromosomes apart
• Telomeres: the end of the chromosomes, protect the end of chromosomes from being mistaken
by the cell for a broken DNA molecule in need of repair
• Each chromosome has multiple origins of replication, one centromere and two telomere
Basic unit of eukaryotic chromosomes:
• Chromatin: complex of both classes of protein (histone & non-histone chromosomal protein)
with the nuclear DNA of eukaryotic cells
• Nucleosome: a protein-DNA complex, with two molecules each of histone H2A, H2B, H3 and
H4, and double stranded DNA that is 147 pairs long
• A histone octamer is the eight protein complex found at the center of a nucleosome core
particle. It consists of two copies of each of the four core histone proteins (H2A, H2B, H3 and
H4).
• Linker DNA between each nucleosome core can vary in length from a few pairs up to 80
• On average, nucleosome repeats at intervals of about 200 nucleotides
• All four histone protein are small (102-135 amino acids), and have the same structural motif
called histone fold, formed from three alpha helices connected by two loops
• N-tail is subjected to several forms of covalent modification
2. Biology Elite biologyelite.weebly.com
• H2A and H2B form a dimer through an interaction called handshake and H3 and H4 forms a
dimer through the same type of interaction
• Two H3-H4 dimer then further combines to form a tetramer.
• An H3-H4 tetramer then combines with two H2A-H2B dimer to form the histone octamer core
where DNA is wound.
• 142 hydrogen bonds are formed between the histone core and the DNA, along with numerous
hydrophobic interactions and salt linkages.
• Nucleosome has a dynamic structure, it will unwrap from each end and recloses thus leaving 10
to 50 milliseconds of free DNA for protein to bind in.
• ATP-Dependent Chromatin remodelling complexes: the arrangement of the nucleosomes on
DNA can be highly dynamic, changing rapidly according to cells’ need.
• By using the energy from ATP hydrolysis, the complexes can reposition nucleosome cores,
remove either all or part of the nucleosome core, make less DNA winding looser
• Packed of nucleosome: Histone tails and histone H1 proteins
• Histone H1 protein presents 1-to-1 ratio with nucleosome cores, and it contacts both the DNA
and nucleosome core. H1 proteins change the path of the DNA as it exits from the nucleosome.
3. Biology Elite biologyelite.weebly.com
Chromatin structure and function:
• Heterochromatin: compact chromatin region that share the common feature of being unusually
resistant to gene expression
• Euchromatin: less condense region of chromatin
• Position effect: euchromatin translocated into the neighbourhood of heterochromatin, which
always causes silencing, inactivation of genes.
• Position effect variegation: once the heterochromatic condition is establish on a piece of
chromatin, it tends to be stably inherited by all of that cell’s progeny
Covalently modified of core histones:
• acetylation of lysines, the mono-, di-, and trimethylation of lysins and the phosphorylation of
serines.
• most of the modification occur on N-terminals of histone tails
• Specific enzymes are responsible for the modification: histone acetyl transferases (HATs) are
responsible for adding of acetyl group and histone deactylase complexes (HDACs) are for
removing acetyl group
• Acetylation of lysine on the N-terminal tails loosens chromatin structure
• Histone modification can also recruit proteins: trimethylation of one specific lysine on the histone
H3 tail attracts the heterochromatin-specific protein HP1 and contributes to the establishment
and spread of heterochromatin
Variants of histone proteins
• those proteins are synthesised and instead into a already formed chromatin, which requires a
histone-exchange process catalysed by the ATP-dependent chromatin remodelling complexes.
4. Biology Elite biologyelite.weebly.com
Covalent modification and histone variants in controlling chromosome functions
• The writer is a enzyme that create a specific modification on one or more of the four nucleosomal
histone
• The writer collaborated with a reader protein to spread its mark from nucleosome to nucleosome
by means of the reader-writer complex
• A similar process is used to remove the histone modification. An eraser protein is recruited to the
complex
• Certain DNA sequences mark the boundaries of chromatin domains and separate one such
domain from another. The sequence is called barrier sequence
• In the case of cells which are destined to give a rise in red-blood cells, a sequence called HS4
normally separate the active chromatin (euchromatin) that contains beta-globin genes. Barrier
sequence in this case contains a cluster of binding sites for histone acetylase enzyme.
Acetylation and methylation of the lysine side chain cannot be performed together and the
methylation are required for the spread of heterochromatin.
• This mechanism stops the spread of reader-writer complex and separate the neighbouring
chromatin
• The chromatin in the centromere contains a centromere-specific variant H3 histone, known as
CENP-A (centromere protein-A)
• In human particularly, centromere also consists of short, repeated DNA sequence called alpha
satellite DNA sequences, but this sequence can be also found in other part of the chromosome,
which indicated they are not sufficient for formation of centromere
5. Biology Elite biologyelite.weebly.com
• In some cases, newly formed human centromere called neocentromere cane formed without
alpha satellite DNA sequence
• Centromeres in complex organism are defined by an assembly of proteins, rather than by
specific DNA sequence.
• Cooperative recruitment of proteins, along with the action of reader-writer complexes, can
not only account for the spreading of specific from of chromatin in space along the chromosome,
but also for its propagation across cell generation.
The structure of chromosome
• Chromosome are folded into large loops of chromatin
• Polytene chromosomes are over-sized chromosomes which have developed from standard
chromosomes and are commonly found in the salivary glands of Drosophila melanogaster.
• Polytene chromosome are viewed under light microscope with dark bands and light interbands.
DNA are more condensed in the dark park and may also contain high concentration of proteins.
• Specific set of non-histone proteins assemble on these nucleosomes to affect biological
function in different ways
• Interphase chromosome can be considered as a chromatin structure containing particular
nucleosome modification associated with a particular set of non-histone proteins.
• Classical heterochromatin contains more than six such proteins, including heterochromatin
protein 1 (HP1)
• Chromatin loops decondense when the genes within them are expressed
6. Biology Elite biologyelite.weebly.com
How genome evolves:
• Homologous genes: genes that are similar in both their nucleotide sequence and fiction
because of a common ancestry
• Conserved sequences are similar or identical sequences that occur within nucleic acid
sequences, protein sequences, protein structures or polymeric carbohydrates across species or
within different molecules produced by the same organism.
• Non-conserved regions will reflect DNA whose sequence is much less likely to be critical for
function
• The only regions that will have remained closely similar in the two genomes are those in which
mutations would have impaired function and put the animals carrying them at a disadvantage,
resulting in their elimination from the population by natural selection. This region is called
conserved region
• Evolution depends on accidents and mistakes followed by nonrandom survival.
• Errors in DNA replication, DNA recombination, or DNA repair can lead either to simple local
changes in DNA sequence—so-called point mutations such as the substitution of one base pair
for another—or to large-scale genome rearrangements such as deletions, duplications,
inversions, and translocations of DNA from one chromosome to another.
• purifying selection is selection that eliminates individuals carrying mutations that interfere with
important genetic functions
• Evolution has followed a pathway requiring the minimum number of mutations consistent with the
data.
• Small blocks of DNA sequence are being deleted from and added to genomes at a surprisingly
rapid rate. Thus, if we assume that our common ancestor had a genome of human size (about
3.2 billion nucleotide pairs), mice would have lost a total of about 45% of that genome from
accumulated deletions during the past 80 million years, while humans would have lost about
25%. However, substantial sequence gains from many small chromosome duplications and from
the multiplication of transposons have compensated for these deletions.
• DNA is added to genomes both by the spontaneous duplication of chromosomal segments that
are typically tens of thousands of nucleotide pairs long (as will be discussed shortly) and by
insertion of new copies of active transposons.