Lecture 28 ErrorsExcepts slides

Lecture 28 ErrorsExcepts slides - Part I: Sex-linked genes...

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Part I: Sex-linked genes Part 2: Errors in inheritance & exceptions to Mendel’s laws Chapter 15 6th ed.: 271-272; 276-282 7th ed.: 282-285; 287
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Autosomes = chromosomes in homologous pairs Sex chromosomes : not always in homologous pairs XX = female (hom. pair) XY = male All eggs; X Sperm: 1/2 X; 1/2 Y
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Other species: different sex chrom’s
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Few genes on Y chromosome Genes on X chromo- some are sex-linked males are hemizygous Drosophila eye color gene is sex-linked
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wild type = red eye mutant = white eye red: (dominant) w+ white: (recessive) w Drosophila eye color studied by Morgan
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white-eye x red-eye all red-eyed P F1 F2 3:1 red:white At first, results look like Mendel’s monohybrid cross
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F2 Total: 3:1 red:white But: results are different for males and females in F2 : 1:1 red: white : all red Explanation: gene is sex-linked
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P generation : is w+ w+, so all eggs are w+ (mutant) is w -, so sperm are half w and half - x chrom. y chrom.
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F1 generation : all are w+ w all are w+ - eggs P F1 (F1; all red-eyed)
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F2 generation : are half w+ w+ and half w+ w are half w+ - and half w - F1 F2
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in humans -color blindness -hemophilia -Duchenne muscular dystrophy -genes on X chrom. -disease allele usually
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This note was uploaded on 06/25/2008 for the course BI 202 taught by Professor Collins/cabot during the Fall '08 term at SUNY Stony Brook.

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Lecture 28 ErrorsExcepts slides - Part I: Sex-linked genes...

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