A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

AcademicBiologyNCERTClass 10

No. From the limited information about having light-colored eyes parents and light-colored eyes children, it cannot be predicted whether the light eye color is a dominant or recessive trait.

However, as both children and parents have light eye color, it is possible that light eye color is a recessive trait. 

If the light-colored eye is a dominant trait, then there are two possibilities

(i) In homozygous light-eyed parents, all the children are light-eyed children,

(ii) In heterozygous light-eyed parents, some of the children can be recessive dark-eyed (3:1 ratio).

Mendel's law of dominance:

In heterozygotes, one trait will suppress the expression of another trait for the same characteristics. 

An allele that expresses its characteristics in all the situations (homozygous or heterozygous) is known as a dominant allele and the allele which is expressed only in its pure form is known as a recessive allele.

Dominant genes are the genes that are expressed in offsprings whether they are present in a heterozygous form (Tt) or homozygous (TT) form.

For example, in the height of the plant, 'T' denotes tallness and 't' denotes dwarfness of the plant. T is dominant over t in the pea plant.

Updated on 10-Oct-2022 13:19:08