Question

The fully dominant and recessive genotypes in the $F_2$ generation of monohybrid cross is

• A. 2/4 each
• B. 1/4 each
• C. 1/16 each
• D. 3/4 each

Answer 1

Answer: (B)

1/4 each

Monohybrid cross refers to inheritance of single contrasting trait by two parents at a time. According to the law of dominance, a monohybrid cross between two pure breeding varieties obtains all dominant $F_1$ generation which in turn produces $F_2$ generation upon selfing. According to the law of segregation, the dominant and recessive alleles present together in $F_1$ hybrid segregate and are delivered singly to gamete to produce two types of gametes i.e. 50% gametes carrying dominant allele and 50% carrying the recessive one. Random fusion of two types of gametes from two $F_1$ hybrid produces monohybrid genotypic ratio of 1 homozygous dominant: 2 heterozygous dominant: 1 homozygous recessive. Thus, the fraction of fully dominant and recessive genotype in $F_2$ generation is ¼ each. Thus, the correct answer is option B.