Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 11 DNA: The Carrier of Genetic Information
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Evidence of DNA as hereditary material Proteins—rather than nucleic acids— thought to be genetic material in the 1930s and 1940s Several lines of evidence supported DNA as genetic material –DNA is transforming principle in bacteria Watson and Crick modeled DNA structure
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Griffith’s transformation experiments Established that DNA carries necessary information for bacterial transformation
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Hershey-Chase experiments Established that viral DNA enters bacterial cells and is required for synthesis of new viral particles
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Structure of DNA Regular polymer of nucleotides –Nitrogenous base of purine or pyrimidine –Base covalently links to deoxyribose –Deoxyribose covalently bonds to a phosphate group Backbone –Alternating sugar and phosphate groups joined by covalent phosphodiester linkages
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Nucleotide subunits of DNA
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Base compositions in DNA from selected organisms
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Structure of DNA molecule Two polynucleotide chains associated as double helix Two chains are antiparallel (running in opposite directions)
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information 3-D model of DNA double helix
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Base-pairing rules for DNA Hydrogen bonding between base pairs holds together the two chains of helix Adenine (A) forms two hydrogen bonds with thymine (T) Guanine (G) forms three hydrogen bonds with cytosine (C) Chargaff’s rules –A = T –G = C
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Base pairing and hydrogen bonding
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information DNA Replication Two strands of double helix unwind Each strand serves as template for new strand DNA polymerase adds new nucleotide subunits Additional enzymes and other proteins required to unwind and stabilize DNA helix
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Enzymes involved in DNA replication
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Simplified view of DNA replication
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Overview of DNA replication
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Leading and lagging DNA strands
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information DNA replication Bidirectional, starting at origin of replication Strands replicate at replication fork Two DNA polymerase molecules catalyze replication –Leading strand –Lagging strand
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Bidirectional DNA replication in bacteria and eukaryotes
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Replication at chromosome ends Telomeres –Short, non-coding repetitive DNA sequences –Shorten slightly with each cell cycles –Can be extended by telomerase –Absence of telomerase activity may be cause of cell aging Most cancer cells have telomerase to maintain telomere length and resist apoptosis
Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 11 DNA: The Carrier of Genetic Information Replication at chromosome ends