Final answer:
In the cross between a yellow summer squash and a green zucchini with genotypes Yy and yy respectively, all offspring would have the genotype Yy and display a yellow phenotype. This results in 100% of the offspring being yellow squash. Option number 4 is correct.
Step-by-step explanation:
The subject of this question is Biology, specifically dealing with genetics and Mendelian inheritance. The scenario involves crossing a summer squash, which has a yellow phenotype determined by a single dominant allele (Y), with a zucchini, which has a green phenotype and thus the genotype yy. We need to predict the outcome of this cross among the offspring.
Since zucchini is green and has the genotype yy, and yellow color in summer squash is due to the genotype being YY (homozygous dominant) or Yy (heterozygous), all offspring from this cross will have one allele from the yellow summer squash and one from the green zucchini, resulting in the genotype Yy. Therefore, all offspring will show the yellow phenotype since the yellow allele (Y) is dominant over the green allele (y).
When you cross a Yy summer squash with a yy zucchini, 100% of the offspring will be Yy and exhibit a yellow phenotype. So, among 60 offspring, you would expect 100% of them to be yellow. This corresponds to selection number 4 from the list provided in the question.