Question

A family consists of two parents and their five children and the pedigree chart below shows the inheritance of the trait colour blindness.
Figure

(i) Who is colour blind in the parents - Father or Mother?
(ii) How many daughters and sons have been born in the family?
(iii) What does the child 1 indicate about this trait?
(iv) Complete the depiction of all probabilities of the trait among the children 2-5 in the chart.
(v) On which chromosome is the gene of this trait located?
(vi) Name one other trait in humans which follows the similar mode of inheritance.

Answer 1

(i) The father is colour-blind.

(ii) Three daughters and two sons have been born in the family.

(iii) Child 1 indicates that she has acquired the disease from her father. She is also colour-blind.

(iv) Children 2 and 4 are carriers of the disease. Child 3 is affected because the mother is also a carrier of the disease, and 50% of the progeny will be affected. Child 5 is normal.

(v) The gene of this trait is located on the X chromosome.

(vi) Haemophilia follows a similar mode of inheritance.