I\'ve heard several times that I need to learn best how to looks atthe genotype

Question

I've heard several times that I need to learn best how to looks atthe genotype of a test cross and be able to predict the phenotypicand genotypic ratios without being able to do a punnett square. Ihave an exam tomorrow and I'm still having problems with looking atthe P1 generation and be able to predict these ratios in both theF1 and the F2. So in this example: A yellow phenotype is dominantto a brown phenotype in sparrows across North America. Skinny wingsare also dominant to fat wings in these same sparrows. If you havea yellow fat winged male that is a heterozygote for the yellowphenotype, and a brown skinny winged female that is a heterozygotefor wing type, what is the projected outcome of both the F1 and theF2?

I just created this question as an example... So when I look atthis I would realize that the father is going to look like this:Ccww (because he is heterozygous for yellow and has fat wings) andthe mother is ccWw. So when looking at the cross: Ccww x ccWw howwould I calculate the offspring without having to do a punnetsquare?

Explanation / Answer

Because the two gene pairs independently assort during gameteformation, we need only calculate the individual probabilities ofthe two separate events (Cc and Ww) and apply the product law tocalculate the final probability.

Chance of being Cc = 1/2

Chance of being Ww =1/2

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