Punnett Square Analysis for Heterozygous Cross

Steps:

• Denote alleles: Y (dominant yellow), y (recessive white); both parents Yy.
• Each parent produces gametes: 50% Y, 50% y.
• Construct Punnett square: Possible zygotes are YY, Yy, Yy, yy.
• Offspring genotypes: 25% YY (homozygous yellow), 50% Yy (heterozygous yellow), 25% yy (homozygous white).

Why C is correct:

• The cross follows Mendel's law of segregation, producing both homozygous dominant (YY, yellow) and homozygous recessive (yy, white) offspring in a 1:2:1 ratio.

Why the others are wrong:

• A: Heterozygous white impossible; white phenotype requires homozygous recessive (yy) by dominance definition.
• B: Produces more than just heterozygous yellow; includes homozygous types.
• D: Produces more than just homozygous yellow; includes heterozygous and homozygous white.

Final answer: C