Question

Suppose that in barley plants, the allele for tall stalks is dominant over short stalks and the allele for wide leaves is dominant over thin leaves. What would be the best way to determine the genotype of a barley plant with a tall stalk and wide leaves? Please choose from one of the following options.

a) Perform a testcross with a barley plant that has a short stalk and thin leaves
b) Perform a testcross with a barley plant that has a tall stalk and wide leaves
c) Perform a testcross with a known heterozygous barley plant
d) Perform a testcross with a barley plant that has a tall stalk and thin leaves

Answer 1

a) perform a testcross with a barley plant that has a short stalk and thin leaves

Step-by-step explanation:

A test cross is a genetic cross wherein an organism expressing dominant traits is crossed with an organism with a homozygous recessive genotype. This is done to know the genotype of the organism expressing the dominant trait. Therefore, to know the genotype of the plant with a tall stalk and wide leaves, it should be test crossed with a plant having a short stalk and thin leaves.

If the obtained progeny contains the plants with short and tall stalks, the dominant parent was heterozygous for this gene. If only tall plants are obtained, the dominant parent was homozygous for the gene.

Similarly, the presence of progeny with both wide and thin leaves suggests that the parent was heterozygous this gene. On the other hand, if obtained progeny has only wide leaves, the dominant parent was homozygous for this gene.