The correct answer is: (A) Female carrier for haemophilia may transmit the disease to sons.
Haemophilia is a genetic disorder that impairs the blood's ability to clot properly. It is an X-linked recessive disease, which means the defective gene causing the disorder is located on the X chromosome. Since males have only one X chromosome (XY), a single defective allele on the X chromosome will result in haemophilia. In contrast, females have two X chromosomes (XX), so a single defective allele typically does not cause the disease in females unless both X chromosomes carry the mutation.
A female who carries the haemophilia gene (heterozygous carrier) may pass on the X chromosome with the defective gene to her children. If she passes this X chromosome with the mutation to a son (who inherits only one X chromosome from his mother), the son will have haemophilia. Therefore, a female carrier of haemophilia has a 50% chance of transmitting the disease-causing allele to her sons.
Thus, the correct statement is that a female carrier for haemophilia may transmit the disease to her sons, as stated in option (A).
List I | List II | ||
A | Down’s syndrome | I | 11th chormosome |
B | α-Thalassemia | II | ‘X’ chromosome |
C | β-Thalassemia | III | 21st chromosome |
D | Klinefelter’s syndrome | IV | 16th chromosome |
Find the incorrect statement among the following: n(A) In sex-linked recessive traits, the gene is transmitted from an unaffected carrier female to some of the male progeny. n(B) Accumulation of phenylpyruvic acid in the brain results in mental retardation. n(C) Individuals affected by Down’s Syndrome will have congenital heart defects and are more intelligent. n(D) Turner’s Syndrome is caused due to the absence of one X chromosome.
List-I | List-II |
(A) Thalassemia | (I) 47, XXY |
(B) Klinefelter’s syndrome | (II) Sex-linked recessive disorder |
(C) Turner’s syndrome | (III) 45, XO |
(D) Colour blindness | (IV) Autosomal recessive disease |