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Lecture 29 Genes are DNA slides

Lecture 29 Genes are DNA slides - Finding that DNA is the...

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Finding that DNA is the Genetic Material Chapter 16 + 17 6th: 287-292; 303-304 & Fig 17.1 7th: 293-298; 309-310 & Fig 17.2
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Mendel found the laws governing inheritance. But HOW are traits passed between generations?
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Morgan (fruit flies) showed “genes” (defined as units governing inheritance of one trait) are on chromosomes. BUT: chromosomes contain DNA and proteins!
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Do proteins carry genetic information? Proteins: the only macromolecules that are structurally diverse VERY simple model organisms answered the question.
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Early evidence for role of DNA in genetics: Griffiths (1928) 2 strains of Strepto- coccus pneumoniae . Only one is pathogenic (causes disease)
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S cells (smooth): have a capsule to avoid the immune system and are pathogenic R cells (rough): no capsule; host kills them (not pathogenic) QUESTION Can the genetic trait of pathogenicity be transferred between bacteria?
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Control experiments : S (live) R (live) S (heat- killed) mouse dies mouse lives mouse lives
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Real experiment: can “pathogenicity- conferring unit” be transferred from DEAD S cells to LIVE R cells mouse dies mixture: live R cells & killed S cells
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Live S cells can be recovered from the dead mouse! (live R & killed S) live S cells!
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Conclusion: genetic information for pathogenicity (capsule formation) was passed from dead S cells to R cells. This is transformation .
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