Mendel1 - 2 2 4 8 2 n No of different genotypes in F 2 3 9 27 3 n Here's what the cross looks like for two of Mendel's traits combined flower color

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Mendel's second law: Law of Independent Assortment Mendel also worked with crosses involving two traits—this is where his luck really entered in. The  traits he picked are on separate chromosomes (though, of course, he didn't know this). Had they  been on the same chromosomes, the ratios he obtained would not have been possible because the  traits would always go together in the same gamete unless some cellular tinkering took place. The mechanisms for figuring out the possible gametes with two traits, filling out the Punnett square,  and counting the possibilities are the same—only with more variations possible (see Table 1  for  potential numbers).  TABLE 1 Possible Two-Trait Genetic Variations Monohybrid Dihybrid Trihybrid n - hybrid No. of different kinds of gametes 2 4 8 2 n Proportion of homozygous recessive F 2 1/4 1/16 1/64 (1/2 n ) 2 No. of different phenotypes F
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Unformatted text preview: 2 2 4 8 2 n No. of different genotypes in F 2 3 9 27 3 n Here's what the cross looks like for two of Mendel's traits combined, flower color and pod characteristics. One allele for each goes in each gamete; purple color (P) is dominant over white (p) flowers, and inflated pods (I) are dominant over constricted (i). Self pollinate the F 1 purple flowered, inflated pod plants and what is the F 2 ratio? Not 3:1 anymore. Fill out a Punnett square and see the possibilities. Each gamete gets one allele of each trait, so a dominant purple (P) can have either a dominant inflated pod (I) or a recessive constricted pod (i); ditto the white (p). Thus, four kinds of gametes are possible: PI, Pi, pI, pi and 4 × 4 combinations are possible from the two parents:...
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This note was uploaded on 11/14/2011 for the course BIO 1421 taught by Professor Farr during the Fall '08 term at Texas State.

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Mendel1 - 2 2 4 8 2 n No of different genotypes in F 2 3 9 27 3 n Here's what the cross looks like for two of Mendel's traits combined flower color

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