Question

When an allele fails to express itself in $F_1$ generation in the presence of other allele, the former is said to be

• A. Recessive
• B. Codominant
• C. Complementary
• D. Epistatic

Answer 1

Answer: (A)

Recessive

• A trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in heterozygous individuals ($F_1$ generation) is called a dominant trait.
• The other factor whose effect is masked by the presence of a dominant factor is called recessive factor. When both recessive and dominant traits are expressed in a heterozygous genotype; it is codominance.
• This means that none of the factors is recessive but both can express themselves irrespective of their presence in homozygous or heterozygous conditions.
• Complementary genes are the nonallelic genes that have their independent effect but produce a new trait when their dominant forms are present together.
• Dominance-recessive inheritance is allelic interaction. Likewise, epistasis refers to the nonallelic interaction wherein one gene masks the expression of another gene present at another locus.

Thus, the correct answer is option A.