WAEC Biology 2019 Papers

Concept:In a complete dominance monohybrid cross, pure breeding parents are homozygous, producing identical heterozygous offspring in the first filial generation.Explanation:The pure yellow-flowered plant is homozygous dominant, represented as $YY$.The pure white-flowered plant is homozygous recessive, represented as $yy$.All gametes from the yellow parent carry the dominant allele $Y$.All gametes from the white parent carry the recessive allele $y$.Fertilisation produces only $Yy$ offspring in the F₁ generation.Since yellow $(Y)$ is completely dominant over white $(y)$, every $Yy$ plant shows the yellow flower phenotype.Therefore, the entire first filial generation consists of yellow-flowered plants.Answer:C. all yellow flowers