Question 1
Multiple choiceEasy1 markIn pea plants, the P generation is YY × yy. F1 plants are self-pollinated to produce F2 plants; assume the gamete combinations are equally likely. The figure shows the F2 Punnett grid. What fraction of F2 zygotes have genotype Yy?
Show answer and explanation
Answer: B. Each zygote combines one allele from a pollen gamete with one allele from an ovule gamete. Two of the four equally likely grid outcomes are Yy, so the fraction is 2/4.
A: counts only one Yy cell, missing the second combination of these alleles.
C: counts the three cells containing at least one Y, rather than only the heterozygous cells.
D: treats every fertilization as producing a heterozygote, overlooking the YY and yy cells.
Remember: each gamete contributes one allele to the zygote.