Kinky hair disease is a disorder where an affected child has peculiar white stubby hair, does not grow, brain degenration 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 from kinky hair disease. Her mother's brother also died of the same condition. Which of the following is the possible mode of inheritance in her family?

Answer is A (X-linked Recessive) : The transmission of disease follows on X-Linked recessive pattern The pedigree analysis reveals the following -Males only are affected by disease - Females are acting as carriers (sister 1 & sister 2) The disease is thus likely to be transmitted through the 'X' chromosome in the mother It is a recessive condition and the mother is a carrier, because if it were a dominant condition, the mother would also manifest the disease. So would sister 1 and sister 2 who carry the affection at least on a single X chromosome as is evident by the affection of male children of both sisters. Males having a single X chromosome (XY) manifest a recessive condition as a disease Also note: females with only one chromosome eg Turner's syndrome can manifest X-linked recessive disorders in the same way as males do.