Question

The cross used to ascertain whether the plant is homozygous or heterozygous is

• A. Linkage cross
• B. Reciprocal cross
• C. Back cross
• D. Monohybrid cross

Answer 1

Answer: (C)

a) A linkage is the tendency of closely placed genes on a chromosome to stay together during inheritance (no crossover and independent assortment). Completely linked genes do not show cross over and independent assortment; thereby produce only parental combinations. Linkage cross is done to deduce the distance between two genes on a chromosome.

b) Two crosses between the same pair of genotypes/phenotypes in which the sources of gametes are reversed in one cross are called reciprocal cross; a cross between yellow and round seed female plant with green wrinkled seed male plant followed by a cross between yellow and round seed male plant with green wrinkled seed female plant. It is done to rule out the possibility of an effect of sex on inheritance pattern.

c) Backcross is cross between $F_1$ hybrid and one of the parents to deduce the genotype of both parents and the hybrid. Monohybrid cross refers to inheritance of singe contrasting trait by two parents at a time. For example: cross of tall (T) and dwarf (t) pea plants is a monohybrid cross as it exhibits the inheritance of plant height (TT x tt).

So, the correct answer is 'Back cross'