biol lec 4

biol lec 4 - We can use a test cross to determine an...

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We can use a test cross to determine an unknown genotype · Also called a back-cross · Cross individual with dominant phenotype (unknown genotype) to homozygous recessive individual · If YY x yy à 100% dominant phenotype (Yy genotype) · If Yy x yy à 50% dominant phenotype (Yy) 50% recessive phenotype (yy) Mendel used a Dihybrid Cross to simultaneously observe the inheritance of 2 traits Mendel observed · Inheritance of sngle traits is the same in mono- and di-hybrid crosses Mendel concluded · Particles for these traits must be inherited independently · Chromosomes containing these genes must move (assort) independently during meiosis There are no rules about how each pair of homologs aligns on the metaphase plate Mendel’s 2 nd law: The law of independent assortment · Alleles at different loci separate independently of one another · Explains why there’s a lot of genetic variation in sexually reproducing species (one individual can make many different types of gametes) Crossing over during Meiosis 1 also increases the # of different types of gametes possible · Allows PARTS of chromosomes to act independently Using the Punnett square to look at Mendel’s Dihybrid cross between the f1s · Determine gametes for parents -handle each locus separately -then multiply to combine in every way possible · Write gamete and frequency along sides of square
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biol lec 4 - We can use a test cross to determine an...

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