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1 03/01/07 BILD1 - Lecture 14 1 BILD1 The Cell Prof. Lisa M. Boulanger 03/01/07 BILD1 - Lecture 14 2 • SPECIAL OFFICE HOURS TODAY 2-4 PM! Problem Set 5 posted tomorrow Discussed in Section next week Regrade requests, in writing, due today! 03/01/07 BILD1 - Lecture 14 3 Pedigree analysis Dominant and recessive disorders Multifactorial disorders Chromosome theory of inheritance Fruit flies Genes associated with specific chromosomes Linkage and failure of independent assortment Recombination of unlinked versus linked Linkage mapping Highlights from previous lecture: 03/01/07 BILD1 - Lecture 14 4 Highlights from previous lecture: Sex-linked genes Recessives on X mostly affect males X inactivation in females Mosaicism in female heterozygotes Changes in chromosome number and structure Aneuploidy (autosome, sex chromosome) Polyploidy Deletions, Duplications, Inversions, Translocations Deviations from Mendel Imprinting, organelle genes 03/01/07 BILD1 - Lecture 14 5 THIS LECTURE: DNA AND HEREDITY, REPLICATION 03/01/07 BILD1 - Lecture 14 6 • Hereditary information – Is encoded in the chemical language of DNA and reproduced in all the cells of your body • It is the DNA program – That directs the development of many different types of traits
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2 03/01/07 BILD1 - Lecture 14 7 The Search for the Genetic Material • Early in the 20th century – The identification of the molecules of inheritance loomed as a major challenge to biologists • The role of DNA in heredity – Was first worked out by studying bacteria and the viruses that infect them 03/01/07 BILD1 - Lecture 14 8 Evidence That DNA Can Transform Bacteria • Frederick Griffith was studying Streptococcus pneumoniae – A bacterium that causes pneumonia in mammals • He worked with two strains of the bacterium – A pathogenic strain and a nonpathogenic strain 03/01/07 BILD1 - Lecture 14 9 • When Griffith mixed heat-killed remains of the pathogenic strain with living cells of the nonpathogenic strain, some of the living cells became pathogenic Smooth (S) = pathogenic Rough (R) = non pathogenic R S Transformed Nonpathogenic Æ Pathogenic 03/01/07 BILD1 - Lecture 14 10 32 P labelled DNA 35 S labelled protein ( Cys & Met a.a.) ( phosphate ) Grow phages with radioactive materials Infect bacteria Separate bacteria and phage by mixing Centrifuge mixture pellet pellet supernatent supernatent Non-radioactive Bacteria 32 P Radioactive bacteria Does viral DNA or protein enter bacteria? DNA has been transferred from phage to bacteria 03/01/07 BILD1 - Lecture 14 11 More evidence for DNA as genetic material Life cycle of bacteriophage Inject DNA into bacteria Hijacks bacteria machinery to copy its own phage DNA and make head and tail proteins Package replicated DNA Lyse bacteria and release new bacteriophages DNA 100 nm 03/01/07 BILD1 - Lecture 14 12 Additional Evidence That DNA Is the Genetic Material • Prior to the 1950s, it was already known that DNA – Is a polymer of nucleotides, each consisting of three components: a
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