Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany.

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Outline 29.1 DNA Carries Genetic Information 29.2 Genetic Information in Bacteria 29.3 Molecular Mechanism of Recombination 29.4 The Immunoglobulin Genes 29.5 Molecular Nature of Mutation 29.6 RNA as Genetic Material 29.7 Transgenic Animals

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company The Transforming Principle is DNA Griffith in 1928 injected bacteria into mice Combination of heat-killed type S and non-virulent type R killed the mice Showed that type S had been transformed by the type R! In 1944, Oswald Avery showed that the active transforming agent was DNA!

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Further Proof In 1952, Hershey and Chase, studying bacteriophages, labelled DNA with 32 P and protein with 35 S Bacteriophage progeny produced by infection of bacteria contained 32 P (thus DNA from the original phage), but not 35 S (from the protein)!

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Genetic Information Can Be Transferred Between Bacteria In 1946, Lederberg and Tatum showed that two different strains of bacteria with different growth requirements could exchange genes Lederberg and Tatum surmised that the bacterial cells must interact with each other - the process is now known as sexual conjugation

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Chromosome Mapping by Interrupted Mating Passage of the ‘F factor’ from Hfr cells to F - cells also brings adjacent genes Genes from the Hfr chromosome are transferred in a fixed order This order can be mapped by ‘interrupted mating’ methods The genetic map obtained reveals a circular arrangement of genes

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Mechanism of Recombination General recombination: any pair of homologous DNA segments as substrates In 1964, Robin Holliday proposed a model involving single-stranded nicks at homologous sites Duplex unwinding, strand invasion and ligation create a Holliday junction

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Enzymology of Recombination RecBCD initiates recombination in E.coli RecA forms nucleoprotein filament for strand invasion and homologous pairing RuvA, RuvB, RuvC drive branch migration and process the Holliday junction into recombination products Eukaryotic systems are probably similar

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company The RecA Protein 38 kD enzyme that catalyzes ATP- dependent DNA strand exchange, leading to formation of Holliday junction RecA forms a helical filament with a groove to accommodate DNA RecA:ssDNA complex binds dsDNA at secondary site and searches for regions homologous with the bound ssDNA, then forms the desired duplex

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Resolving Holliday Junctions Ruv proteins resolve the junction into recombination products RuvA and RuvB act as a helicase that dissociates the RecA filament and catalyzes branch migration RuvC is an endonuclease that binds at the junction and cuts pairs of DNA strands of similar polarity. Splice and patch recombinants result.

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Transposons In 1950, Barbara McClintock showed that activator genes in corn could move freely about the genome. This was at first viewed as heresy and McClintock was ostracized Molecular biologists in the late 1970s rediscovered what McClintock knew She received a MacArthur Award in 1981 and a Nobel in 1983

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Immunoglobulin Genes Immunoglobulin genes maximize protein diversity with a limited amount of genetic information DNA rearrangement (genetic recombination) during assembly of IG genes accounts for this diversity Three separate genes are combined to form the L-chain gene Four genes combine to form H-gene

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Molecular Nature of Mutation Point mutations - one base for another - arise from mispairing, insertion of analogs or chemical mutagens Mutagens include nitrous acid, hydroxylamine and alkylating agents Insertions and deletions result in frameshift mutations

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Prions Proteins as Genetic Agents? Prions are ‘protein infectious particles’ Agents composed only of protein Responsible for kuru, Creutzfeld-Jacob disease, mad-cow disease, etc. The ‘infection’ appears to involve a change of secondary structure and conformation (or conformations!) in the prion protein A Nobel for Stanley Prusiner in 1997

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company Transgenic Animals Genes can be introduced into animals by transfection - injection of plasmid DNA into recipient cells Plasmids can be injected into fertilized eggs in mice Expression is usually variable, because the gene is inserted randomly Growth hormone transfection produces mice that are very large!

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany.

Similar presentations

Presentation on theme: "Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany.

Similar presentations

Presentation on theme: "Biochemistry 2/e - Garrett & Grisham Copyright © 1999 by Harcourt Brace & Company CHAPTER 29 DNA: Genetic Information, Recombination, and Mutation to accompany."— Presentation transcript:

Similar presentations

About project

Feedback