WAEC Biology 2012 Papers

Concept:A hybrid yellow plant carries one dominant yellow allele and one recessive green allele, so both parents have the genotype $Yy$.Explanation:Let $Y$ represent the dominant allele for yellow flowers.Let $y$ represent the recessive allele for green flowers.Each parent is hybrid yellow, so the genotype of each parent is $Yy$.Cross the two parents: $Yy \times Yy$.The possible offspring genotypes are $YY$, $Yy$, $Yy$, and $yy$.Only the genotype $yy$ produces green flowers.Thus, 1 out of every 4 offspring will have green flowers.Answer:The correct proportion is $1$ in $4$, which is option C.