Question

ry
rryy
ry
the correct parents of the cross above are...
rrrr x rryy
rryy x rryy
rryy x rryy
rryy x rryy

Explanation:

Step1: Identify gamete types

The Punnett square shows only two gamete types: $RY$ and $ry$.

Step2: Match to parental genotypes

A parent with genotype $RRYY$ can only produce $RY$ gametes (homozygous dominant for both traits). A parent with genotype $rryy$ can only produce $ry$ gametes (homozygous recessive for both traits). Their cross will only yield $RrYy$ offspring, matching the Punnett square.

Step3: Eliminate other options

• $RrYY \times RRYy$ produces multiple gamete combinations, not just $RY/ry$.
• $RrYy \times RrYy$ produces 4 gamete types, resulting in more Punnett square combinations.
• $rrYY \times RRyy$ produces $rY$ and $Ry$ gametes, not $RY/ry$.

Answer:

C. $RRYY \times rryy$