2_Chromosomes

2_Chromosomes - 2) Inheritance of chromosomes and DNA 15.1...

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1 2) Inheritance of chromosomes and DNA 15.1 - 15.3 and 16.1
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2 We now know that Mendel’s “hereditary factors” are located on chromosomes
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3 Early studies of meiosis showed that the behavior of chromosomes parallels the behavior of Mendel’s “factors” Both chromosomes and “factors” Present in pairs in diploid cells Segregate during meiosis Halve their copy numbers during meiosis and double their copy numbers at fertilization
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4 Thomas Hunt Morgan’s fruit fly experiments provided first strong evidence that genes are on chromosomes
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5 Why fruit flies? Easy to rear in lab Short generation time (~10d) Abundant offspring (100s per mating) Only 4 pairs of chromosomes Numerous mutation stocks now available
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6
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P Generation F 1 Generation F 2 Generation
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P Generation F 1 Generation F 2 Generation P Generation F 1 Generation Ova (eggs) Sperm F 2 Generation Ova (eggs) Sperm Morgan’s explanation
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9 What happens when genes are located on the same chromosome? Morgan noticed that certain traits tended to be inherited together
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P Generation (homozygous) Parental-type offspring Double mutant (black body, vestigial wings) Recombinant (nonparental-type) offspring b b vg vg Double mutant (black body, vestigial wings) b b vg vg Ova Sperm TESTCROSS 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Wild type (gray body, normal wings) b + b + vg + vg + F 1 dihybrid (wild type (gray body, normal wings) b + b vg + vg
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Parents in testcross Most offspring or
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This note was uploaded on 02/19/2008 for the course BISC 120Lg taught by Professor 11:00-01:50pm during the Fall '06 term at USC.

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2_Chromosomes - 2) Inheritance of chromosomes and DNA 15.1...

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