Unit 2 Notes

Unit 2 – Mechanisms of Inheritance

Molecular Basis of Inheritance Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene Take A Tour (Can be found in the outbox)

Molecular Basis of Inheritance The blueprint for the development and appearance of each individual is contained within the chromosomes of our cells. All of this information is efficiently organized and tightly packed into pairs of chromosomes located inside the cell nucleus. Chromosomes are made up of a molecule called DNA (deoxyribonucleic acid ) Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

Molecular Basis of Inheritance Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

A Model of DNA In 1953, James Watson (American) and Francis Crick (British) developed a model of the structure of DNA. DNA is the largest molecules in a living organism but is composed of much simpler units. The DNA model has been described as a ladder. The rungs are solid and the sides are flexible. By twisting the ladder from each end you can form a spiral or helix. A double spiral can be formed and is called a double helix . The DNA molecule has the shape of a double helix. Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

A Model of DNA There are three basic units that link together to make the ladder. Phosphate groups and sugars (deoxyribose) form the sides of the ladders and the rungs are made from larger molecules called nitrogen bases . There are four bases found in DNA. They are adenine, thymine, guanine, and cytosine . They are represented by the letters, A, T, G, and C . The combination of one phosphate group, one sugar, and one nitrogenous base is called a nucleotide . Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

A Model of DNA Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

A Model of DNA A bond can form between the phosphate group of one nucleotide and the sugar of another nucleotide to form a chain of nucleotides. Watson and Crick also found that weaker bonds ( hydrogen bonds ) may also form between the nitrogenous bases of the nucleotides Because of there structures, adenine can only bond with thymine, and cytosine can only bond with guanine. Thus there are only four base pair combinations present in DNA. These are: A-T T-A G-C C-G Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

A Model of DNA The position of these base pairs in the rung is very important because the bases carry hereditary information in coded form. The code depends upon the arrangement of these bases in DNA. When two chains of nucleotides combine, they form a double helix structure of DNA. The DNA of a single chromosome may contain 6 million turns and measure 2.2 cm long when fully extended. The double helix shape enables the chromosome to be tightly coiled for transfer during cell division. Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

The Genetic Code The genetic code is the relationship between the sequence of the bases in the DNA and the sequence of amino acids in proteins. The sequence of bases in DNA codes for the sequences of amino acids in proteins. However, there are 20 amino acids found in proteins and only 4 different bases found in DNA. At least 3 bases in combination as a triplet are required to code for each amino acid and this would give 4 to power 3 = 64 possible combinations of triplet bases or codons. We now know that the genetic code is based on these triplet codons. Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

The Genetic Code All 64 codons are known and 61 triplets correspond to particular amino acids the other 3 triplets code for chain termination to liberate proteins at the end of the synthesis of a protein. Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

The Genetic Code Outcome 2-02 Describe the structure of a DNA nucleotide. Include: deoxyribose sugar, phosphate group, nitrogenous bases. Outcome 2-03 Describe the structure of the DNA molecule. Include: double helix, nucleotides, base-pairing, gene

DNA Replication When Watson and Crick developed their model of DNA structure, they immediately recognized that the complementary nature of the two sides of the helix could provide a mechanism for accurate DNA replication. Given your knowledge of DNA structure, can you propose a mechanism for accurate DNA replication? Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes Copying the Code: examining the evidence

DNA Replication To reproduce, a cell must copy and transmit its genetic information (DNA) to all of its progeny. Replication of DNA Occurs during S phase of the cell cycle Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication DNA replication is semi-conservative . Each strand of the original DNA molecule acts as a template for the synthesis of a new complementary DNA molecule. Each daughter DNA molecule consists of one new chain of nucleotides and one from the parent DNA molecule The 2 daughter DNA molecules will be identical to the parent molecule Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication Before replication begins, the 2 strands of the parent molecule are hydrogen-bonded together. Enzyme helicase unwinds and “unzips” the double-stranded DNA New DNA nucleotides fit into place along divided strands by complementary base pairing New nucleotides form bonds with the existing ones- DNA polymerase DNA polymerase is described as being "template dependent" in that it will "read" the sequence of bases on the template strand and then "synthesize" the complementary strand. Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication The template strand is ALWAYS read in the 3' to 5' direction (that is, starting from the 3' end of the template and reading the nucleotides in order toward the 5' end of the template). The new DNA strand (since it is complementary) MUST BE SYNTHESIZED in the 5' to 3' direction. DNA polymerase catalyzes the formation of the hydrogen bonds between each arriving nucleotide and the nucleotides on the template strand. Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication DNA ligase repairs any breaks in the sugar-phosphate backbone Two daughter DNA molecules have now formed that are identical to the original Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

DNA Replication Two strands of DNA are obtained from one, having produced two daughter molecules which are identical to one another and to the parent molecule. Outcome 2-04 Describe the process of DNA replication. Include: template, semi-conservative replication, role of enzymes

RNA (ribonucleic acid) The DNA is too valuable for the cell to use directly for protein synthesis. The DNA remains in the nucleus as a master copy and instead working copies of the required segments (RNA) are sent into the surrounding cytoplasm of the cell to make a protein. These smaller segments are called ribonucleic acid (RNA). Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

RNA (ribonucleic acid) RNA Composed of nucleotides Each nucleotide has 3 parts Phosphate Sugar- ribose 4 possible nitrogen bases Adenine and guanine Cytosine and uracil Note that uracil replaces thymine 3 major classes of RNA mRNA- carries genetic information from the DNA out to ribosomes rRNA- composes ribosomes, site of protein assembly tRNA- brings in amino acids to the ribosomes Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

RNA (ribonucleic acid) Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

RNA Transcription Transcription is the process in living cells whereby RNA is synthesized from a template of a single strand of DNA. In doing so, the genetic information is converted from one nucleic acid into another, that is, from DNA to RNA. To form RNA, DNA is unzipped by enzyme (RNA polymerase) action. This exposes the nitrogen bases which act as a pattern or template for the information of RNA. An enzyme called RNA polymerase is responsible for creating a strand of RNA from a strand of DNA. This RNA is specifically called messenger RNA (or mRNA) because it carries the genetic message from the nucleus to the cytoplasm. Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

RNA Transcription Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

RNA Transcription Transcription Segment of DNA serves as a template for production of mRNA Messenger RNA (mRNA) RNA polymerase binds to a promoter DNA helix is opened so complementary base pairing can occur RNA polymerase joins new RNA nucleotides in a sequence complementary to that on the DNA Outcome 2-05 Compare DNA and RNA in terms of their structure, use and location in the cell

Protein Synthesis Proteins are molecules made from chains of individual amino acids. Some proteins are small, with only 20 or so amino acid units. Others are large molecules with thousands of amino acid. There are only 20 different kinds of amino acids. To create all the different kinds of protein molecules, the amino acids are arranged in a specific order. It is the sequence and length of amino acids that determines the kind of protein. The sequence of nitrogen bases on a DNA strand determines the sequence of amino acids in a protein molecule. It takes three nitrogen bases to "code" for one amino acid. A segment of these three bases is called a triplet. The equivalent triplet on a mRNA is called a codon. Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Protein Synthesis Since there are four different nitrogen bases, there are 64 possible triplet combinations. The arrangement of codons along the mRNA constitutes the genetic code. When synthesis of a given protein is necessary, the segment of DNA with the appropriate base sequences is transcribed into messenger RNA. When the mRNA moves to the ribosome, its sequence of codons is paired with anticodons in transfer RNA. Each tRNA carries one amino acid and attaches it to a string of other amino acids. Eventually, this chain of amino acids becomes a complete protein. Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Translation Translation is the process where the genetic code of messenger RNA is deciphered to make proteins. Actually, the products of translation are chains of polypeptides, or incomplete protein molecules. Each polypeptide chain is released from the ribosome and can undergo further reactions in the cell to complete a fully functional protein. Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Translation Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Translation The genetic code Triplet code - each 3-nucleotide unit of a mRNA molecule is called a codon There are 64 mRNA codons 61 code for particular amino acids Redundant code -some amino acids have numerous code words 3 are stop codons signal polypeptide termination One codon stands for methionine-signals polypeptide initiation Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

mRNA Codons Outcome 2-06 Compare DNA and RNA in terms of their structure, use and location in the cell

Translation Transfer RNA (tRNA) tRNA transports amino acids to the ribosomes Single stranded nucleic acid that correlates a specific nucleotide sequence with a specific amino acid Amino acid binds to one end, the opposite end has an anticodon the order of mRNA codons determines the order in which tRNA brings in amino acids Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Translation Transfer RNA (tRNA) Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Stages of Translation The first stage is called initiation , in which mRNA at a ribosome codes for the first amino acid in a sequence of polypeptides. The next stage is called continuation or elongation . Here, the peptide chain is built up using amino acids transferred by tRNA. As each pair of tRNA's occupies a site at a ribosome, the amino acids are joined by a peptide bond. As the ribosome moves along the mRNA to the next codon, the next tRNA brings along its amino acid and creates a peptide bond. Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Stages of Translation This process continues until the ribosome encounters a termination codon, the code for the last amino acid in the peptide chain. This last stage is called termination --when the protein molecule or polypeptide chain is complete and is released from the ribosome. Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

Protein Synthesis Outcome 2-06 Outline the steps involved in protein synthesis. Include: mRNA, codon, amino acid, transcription, tRNA, anticodon, ribosome, translation

What is a mutation? A mutation is a permanent change in the DNA sequence of a gene. Mutations in a gene's DNA sequence can alter the amino acid sequence of the protein encoded by the gene. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

What is a mutation? T hink about the DNA sequence of a gene as a sentence made up entirely of three-letter words. In the sequence, each three-letter word is a codon , specifying a single amino acid in a protein . Have a look at this sentence. Thesunwashotbuttheoldmandidnotgethishat. The sun was hot but the old man did not get his hat. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

What is a mutation? Does this sentence make sense? T hes unw ash otb utt heo ldm and idn otg eth ish at. or Th esu nwa sho tbu tth eol dma ndi dno tge thi sha t. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

What is a mutation? http://highered.mcgraw-hill.com/sites/0070271348/student_view0/chapter13/elearning.html Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Point Mutations Point mutations are single nucleotide base changes in a gene's DNA sequence. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Point Mutations Point mutations can change the gene's protein product in the following ways: Missense mutations Nonsense mutations Silent mutations Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Missense Mutations With a missense mutation, the new nucleotide alters the codon so as to produce an altered amino acid in the protein product. EXAMPLE: sickle-cell disease The replacement of A by T at the 17th nucleotide of the gene for the beta chain of hemoglobin changes the codon GAG (for glutamic acid ) to GTG (which encodes valine ). Thus the 6th amino acid in the chain becomes valine instead of glutamic acid. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Nonsense Mutations With a nonsense mutation, the new nucleotide changes a codon that specified an amino acid to one of the STOP codons ( TAA , TAG , or TGA ). Therefore, translation of the messenger RNA transcribed from this mutant gene will stop prematurely. The earlier in the gene that this occurs, the more truncated the protein product and the more likely that it will be unable to function. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Silent Mutations Most amino acids are encoded by several different codons . For example, if the third base in the TCT codon for serine is changed to any one of the other three bases, serine will still be encoded. Such mutations are said to be silent because they cause no change in their product and cannot be detected without sequencing the gene (or its mRNA). Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Frameshift Mutations Insertion mutations and deletion mutations add or remove one or more DNA bases. Insertion and deletion mutations cause frameshift mutations , which change the grouping of nucleotide bases into codons. This results in a shift of "reading frame" during protein translation. Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Frameshift Mutations Outcome 2-07 Relate the consequences of gene mutation to the final protein product. Examples: point mutation, frameshift mutation

Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies.

Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Genetic Engineering

The direct introduction of foreign genes into an organism's genetic material by micromanipulation at the cell level is referred to as genetic engineering . Think of recombinant DNA as "recombining" segments of genes. A fragment of DNA or gene is taken from a cell and reinserted into another segment of gene in another cell. Recombination can occur naturally, but in genetic engineering it is artificially constructed. The cell that inherits the new DNA segment will have traits that are different from its parents. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Genetic Engineering

Some bacteria have special properties that allow scientists to do more research on recombinant DNA . These bacteria have molecules called plasmids . Plasmids consist of DNA molecules but they are not part of the DNA of the regular chromosomes. The plasmid can therefore reproduce itself without the help of other chromosomes involved in cell division. Because of this, plasmids can transfer genetic material from one cell to another and add new traits to the cell. As these cells reproduce, they also reproduce new genetic material. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Recombinant DNA

How do geneticists "cut" segments of DNA? They use enzymes called restriction enzymes . It is the discovery of these enzymes that led the way to genetic engineering and advances in biotechnology. Most research on recombinant DNA comes from experiments using bacteria, because bacteria reproduce quickly and are easy to grow in the lab. Scientists take a DNA segment and splice it into the DNA of another bacterium. This is called bacterial transformation . The bacteria with the new segments of DNA produce new substances because they have acquired characteristics from the spliced gene. They have been permanently transformed into "new" bacteria. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Restriction Enzymes

Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Gene Splicing

Plasmids that carry a spliced gene into a foreign cell are called vectors . Several types of vectors are used in gene cloning, but the most common vectors are those found in bacteria. A bacterial cell usually has regular chromosomes shaped as a large circle. There are also smaller, circular pieces of DNA called plasmids. The plasmids replicate independently of the main DNA and have different genetic instructions. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Plasmids as Vectors

After a plasmid is removed from the bacterial cell, a segment of it is "cut" by special enzymes called restriction enzymes . The "cut" is caused by the action of enzymes that break the bonds between molecules. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Plasmids as Vectors

The DNA fragment from another cell, for example from a frog or an insect, is then attached or spliced into the plasmid. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Plasmids as Vectors

The new plasmid is called recombinant DNA, and it has different genetic instructions. It is reintroduced into the same bacterium. This bacterium is now called a host. Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies. Plasmids as Vectors

As the bacterial cell replicates, it will also replicate the plasmid. Plasmids as Vectors Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies.

Biotechnology Transgenic bacteria Contain a recombinant gene which is then cloned and expressed Product can be collected from medium the bacteria are grown in Transgenic bacteria have been developed for many uses Transgenic plants Insert new genes into protoplasts-plant cells with cell walls removed Can make plants insect-resistant, disease-resistant, etc. Can “pharm” plants to produce human proteins Transgenic animals Genes inserted into animal eggs Can increase size of animals Can “pharm” animals to produce drugs in milk Transgenic Organisms Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies.

DNA fingerprinting Permits identification of individuals and their relatives Based on differences between sequences in nucleotides between individuals Detection of the number of repeating segments (called repeats) that are present at specific locations in DNA DNA Finger-printing Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies.

Human Genome Project http://www.dnai.org/c/index.html Outcome 2-09 & 2-10 Investigate an issue related to the application of gene technologies.

Unit 2 Notes

More Related Content

What's hot

Viewers also liked

Similar to Unit 2 Notes

More from Bruce Coulter

Recently uploaded

Unit 2 Notes