Kinky hair desease is disorder where an affected child has peculiar white stubby hair, does not grow, brain degeneration is seen and dies by age of two years. Mrs A is hesitant about having children because her two sisters had sons who had died form kinky hair disease. Her mother's brother also died of the same condition. Which of the following is the possible mode of inheritence in her family -
Ans. is 'a' i.e., X-linked Recessive o The clues in this question are ? Only males are manifesting disease. Females are acting as carriers -3 sisters sons had suffered from the disease. o Both these are features of X-linked recessive disorders. X-linked disorders o Except for a few conditions, all X-linked disorders are X-linked recessive. o As male has only one X-chromosome, the male with affected gene on X-chromosome will always manifest the disease. o On the other hand, female has 2 X-chromosomes, heterozyogous female will be carrier because of expression of normal allel on the other X-chromosome. o Note ---> Female with Turner syndrome (only one 'X' chromosome) can manifest X-linked recessive disorders. o 50% boys of the carrier mother will be affected. o All daughters of affected father will become carrier, i.e. affected father will transmitt the defective X chromosome to all the daughters. o Father will not transmitt the disease to son as boys do not inherit X-chromosome from father. About other options o In X-linked dominant disorder the females will also manifest the disease. o In autosomal dominant and autosomal recessive disorders, both males and females are affected.
X-linked recessive
X-linked dominant
Autosomal recessive
Autosomal dominant