lecture 4 - Trait 1 Pku Trait 2 albinism pp mm Cross: no...

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I. Who was Mendel? II. Physical structure of the genome III. What did Mendel figure out? IV. Sex determination and the behavior of sex linked traits Mendel’s first law: segregation a gamete receives only 1 allele for each gene (even though the organism generally has two) fertilization reestablishes the diploid number. P1 (parents’) phenotypes Albino normal mm MM ]—genotypes m m M M ]—gametes F1 (offspring) Genotypes: mM Phenotypes: normal Gametes: m M What happens if we cross the F1s? F1 Cross: mM x mM Punnett square to produce Mm, mm, MM, and Mm (female gametes always on top, male gametes always on the side) What are the genotype ratios? 1 MM: 2 Mm: 1 mm What are the phenotype ratios? 3 normal: 1 albino Take home message 1: The law of segregation points out that a gamete receives only one allele from the pair of alleles possessed by an organism Q: Do we expect many human traits to be controlled by a single gene? Yes Mendel’s Second law: Independent assortment
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Unformatted text preview: Trait 1 Pku Trait 2 albinism pp mm Cross: no pku, no albinism x pku, albino Genotypes: PP MM x pp mm Gamete: PM pm F1 offspring? PpMm Gametes? PM Pm pM pm The dihybrid punnett square Take home message 2: The allele you pass on for one trait has no effect on which allele you pass on for some other trait (independent assortment) Q: if an individual shows the dominant phenotype, how can you determine their genotype? Take home message 3: The test cross allows you to determine whether inds showing the dominant trait are homozygous or heterozygous Sex determination How is the sex of a baby determined by the father? Q: if men only have one x chromosome, are they more or less likely to exhibit a sex link a sex-linked recessive trait? What about dominant? Take home message 4: Sex linked traits have different patterns of expression in males and females...
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lecture 4 - Trait 1 Pku Trait 2 albinism pp mm Cross: no...

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