Question

Two heterozygous parents:

_______% gametes with allele R
_______% gametes with allele r

______% gametes with allele R
_______% gametes with allele r

________ fuse ________ to make the _______ generation.

Answer 1

The law of segregation and independent assortment determine the genotypic and phenotypic ratios in the F2 generation.

Step-by-step explanation:

For the F2 generation, the law of segregation requires that each gamete receive either an R allele or an r allele along with either a Yallele or a y allele. The law of independent assortment states that a gamete into which an rallele sorted would be equally likely to contain either a Yallele or a y allele. Thus, there are four equally likely gametes that can be formed when the YyRr heterozygote is self-crossed, as follows: YR, Yr, yR, and yr. Arranging these gametes along the top and left of a 4 × 4 Punnett square (Figure 12.16) gives us 16 equally likely genotypic combinations. From these genotypes, we infer a phenotypic ratio of 9 round/yellow:3 round/green:3 wrinkled/yellow:1 wrinkled/green (Figure 12.16). These are the offspring ratios we would expect, assuming we performed the crosses with a large enough sample size.