Q.112. Study the pedigree chart given below :-
What does it show -
(1) Inheritance of a recessive sex-linked disease like haemophilia
(2) Inheritance of a sex-linked inboron error of metabolism like phenyl ketoneuria.
(3) Inheritance of a condition like cystic fibrosis as an autosomal recessive trait
(4) The pedigree chart is Y-linked Inheritance
When the gene causing trait or disorder is located on the X chromosome, then it is known as X-linked inheritance. Females have two X chromosomes; males have one X and one Y. Genes on the X chromosome can be recessive or dominant.
X-linked recessive genes are expressed in females only if there are two copies of the gene (one on each X chromosome). On the other hand, in males, it needs only one copy of an X-linked recessive gene to express the trait.
A carrier woman can carry a recessive gene on one of the X chromosomes which can be pass on to a son, who will express the trait.
Similarly given pedigree chart shows x-linked recessive inheritance which can be observed in disorders like Colorblindness, Haemophilia, Duchenne muscular dystrophy etc.
In F1 generation, 1 male and 1 female are diseased and in next generation, only 1 male is diseased.
Option (1) Inheritance of a recessive sex-linked disease like haemophilia , is the correct answer.