Biology 105 Chapter 12: DNA - The Carrier of Genetic Information Pages Chapter 12: DNA - The Carrier of Genetic Information Pages

Student Outcomes Summarize the discovery of the DNA structure in the ’s Sketch how nucleotides link together to form a DNA strand Summarize the process of how DNA replicates. Summarize the discovery of the DNA structure in the ’s Sketch how nucleotides link together to form a DNA strand Summarize the process of how DNA replicates.

Student Outcomes Explain the connections between telomerase and cell aging and cancer.

DNA as genetic material Transformation - process of changing the genetic makeup of an organism by an another organism. Viruses are now used to introduce changes in DNA of the host Transformation - process of changing the genetic makeup of an organism by an another organism. Viruses are now used to introduce changes in DNA of the host

DNA structure In Watson and Crick proposed the double helix model of DNA DNA is made of a nucleotide: deoxyribose - sugar phosphate 1 of 4 nitrogenous bases In Watson and Crick proposed the double helix model of DNA DNA is made of a nucleotide: deoxyribose - sugar phosphate 1 of 4 nitrogenous bases

Nitrogenous bases Two Types Purines Adenine (A) Guanine (G) Pyrimidines Thymine (T) Cytosine (C) The ratio of Purines to Pyrimidines is equal Hydrogen bonds form between them. Two Types Purines Adenine (A) Guanine (G) Pyrimidines Thymine (T) Cytosine (C) The ratio of Purines to Pyrimidines is equal Hydrogen bonds form between them.

DNA Replication Known as semi-conservative replication. DNA strands break at the hydrogen bonds(unzips). Each separate strand becomes a template for the other. This type of replication allows mutations to continue once they occur. Known as semi-conservative replication. DNA strands break at the hydrogen bonds(unzips). Each separate strand becomes a template for the other. This type of replication allows mutations to continue once they occur.

DNA replication continued Each strand must untwist and unzip. Controlled by enzymes known as DNA helicases. SSB’s then stabilize the DNA so that it doesn’t recoil. (single-strand binding proteins) DNA polymerases catalyze the linking of the new nucleotides. Each strand must untwist and unzip. Controlled by enzymes known as DNA helicases. SSB’s then stabilize the DNA so that it doesn’t recoil. (single-strand binding proteins) DNA polymerases catalyze the linking of the new nucleotides.

DNA replication continued An RNA primer is needed at the beginning point of DNA replication. This primer is synthesized by DNA primase The RNA primer is later filled in with DNA An RNA primer is needed at the beginning point of DNA replication. This primer is synthesized by DNA primase The RNA primer is later filled in with DNA

Telomeres End caps of chromosomes These are short noncoding DNA repeats Each time DNA replicates (a cell duplicates itself) part of the telomere does not replicate and is lost. DNA can replicate many times. However, eventually important and essential coding DNA may be lost End caps of chromosomes These are short noncoding DNA repeats Each time DNA replicates (a cell duplicates itself) part of the telomere does not replicate and is lost. DNA can replicate many times. However, eventually important and essential coding DNA may be lost

Cell Aging Telomerase is a DNA replication enzyme which can lengthen the Telomeres. Somatic cells do not have this but germ cells do. Shortening of telomeres contribute to cell aging and cell death Cancer cells have the DNA Telomerase which allows many uncontrolled replications. Telomerase is a DNA replication enzyme which can lengthen the Telomeres. Somatic cells do not have this but germ cells do. Shortening of telomeres contribute to cell aging and cell death Cancer cells have the DNA Telomerase which allows many uncontrolled replications.

Chromosomal mutations Occur in either mitosis or meiosis 4 types: Deletion Inversion Translocation Nondisjunction Occur in either mitosis or meiosis 4 types: Deletion Inversion Translocation Nondisjunction

Gene Mutations Detectible and heritable change in the genetic material - not caused by genetic recombination! Occurs at the gene level. Caused by Mutagens - physical or chemical agent Detectible and heritable change in the genetic material - not caused by genetic recombination! Occurs at the gene level. Caused by Mutagens - physical or chemical agent

Gene Mutations Base-Pair Substitution Mutation AT is replaced with a GC Three types: Missense-the change results in a different codon Nonsense-the change results in an ending codon UAC, UAA, UGA Neutral - change does not result in a different amino acid Base-Pair Substitution Mutation AT is replaced with a GC Three types: Missense-the change results in a different codon Nonsense-the change results in an ending codon UAC, UAA, UGA Neutral - change does not result in a different amino acid

Gene Mutations Frameshift mutation –The addition or deletion of a base pair of a gene Frameshift mutation –The addition or deletion of a base pair of a gene