Question
Explain dominant, recessive characters and phenotypic and genotypic characters through Mendel’s monohybrid cross.
Answer
Mendel’s monohybrid cross was conducted between pea plants having one pair of contrasting characters, for example, tall (dominant) and dwarf (recessive). Here, ‘T’ represents the dominant allele for tallness and ‘t’ represents the recessive allele for dwarfness.
When a homozygous tall plant (TT) is crossed with a homozygous dwarf plant (tt), the F1 generation consists of only tall plants (Tt). This indicates that the dominant trait (tallness) is expressed over the recessive trait (dwarfness) in the heterozygous condition (Tt).
In the F2 generation, when the heterozygous tall plants (Tt) are self-pollinated, the genotypic ratio is 1:2:1 (TT:Tt:tt) and the phenotypic ratio is 3:1 (tall:dwarf). This is because during gamete formation, the alleles segregate independently of each other and combine randomly in the zygote, leading to a variety of genotypic and phenotypic ratios.
