WAEC Agriculture 2011 Paper

Concept:A monohybrid cross between two heterozygous tall plants ($\mathrm{Tt} \times \mathrm{Tt}$) produces the $F_2$ generation with a predictable genotypic ratio.Explanation:Tallness ($T$) is dominant over dwarfness ($t$).The $F_1$ generation from a cross between pure tall ($TT$) and dwarf ($tt$) is all heterozygous tall ($\mathrm{Tt}$).Self-pollination of the $F_1$ plants gives the cross $\mathrm{Tt} \times \mathrm{Tt}$.Each parent produces two types of gametes: $T$ and $t$.Fertilisation results in the following $F_2$ genotypes: $TT$, $Tt$, $Tt$, and $tt$.Thus, the genotypic ratio is $1 : 2 : 1$.Answer:B. $1:2:1$