CBSE Class 10 Science 2022 · Paper 31/3/1 · Question 6(a)

Each characteristic is controlled by a pair of factors (genes), one inherited from each parent. When Mendel crossed a pure tall plant ($TT$) with a pure short plant ($tt$), every ${\text{F}}_1$ plant received one factor for tallness and one for shortness ($Tt$). Tallness is the dominant trait and shortness the recessive one, so in each ${\text{F}}_1$ plant only the dominant trait was expressed and all the plants were tall. The two factors do not blend, so no half-way (medium-height) plants appeared; the recessive factor was not lost either, because short plants reappeared in the ${\text{F}}_2$ generation in the ratio $3$ tall : $1$ short.