Sex-Linked Recessive Haemophilia — NEET Biology
✅ Asked in NEET 2023Haemophilia: This sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny has been widely studied. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected. Due to this, in an affected individual a simple cut will result in non-stop bleeding. The heterozygous female (carrier) for haemophilia may transmit the disease to sons. The possibility of a female becoming a haemophilic is extremely rare because mother of such a female has to be at least carrier and the father should be haemophilic (unviable in the later stage of life). The family pedigree of Queen Victoria shows a number of haemophilic descendents as she was a carrier of the disease.
Haemophilia is a sex-linked recessive trait located on the X chromosome, not a regular Mendelian disorder. NTA tests whether you understand that affected males (X^h Y) inherit it from carrier mothers (X^H X^h), while affected females (X^h X^h) are extremely rare because they need both carrier and affected parents. Students often confuse this with autosomal recessive traits or think females are equally affected. Remember: carrier females can have affected sons; affected females require a haemophilic father and at least carrier mother. Queen Victoria's pedigree is the classic example NTA uses to test pattern recognition of X-linked inheritance across generations.
This paragraph was tested 4 times in NEET.
Which of the following is not an example of a Mendelian disorder? (NEET 2023)
Given below are two statements: Statement I: Sickle cell anaemia and haemophilia are autosomal dominant traits. Statement II: Sickle cell anaemia and haemophilia are disorders of the blood. In the light of the above statements, choose the correct answer from the options given below: (NEET 2022)
Pick out the correct statements. (NEET 2016) (1) Haemophilia is a sex-linked recessive disease. (2) Down’s syndrome is due to aneuploidy. (3) Phenylketonuria is an autosomal recessive gene disorder. (4) Sickle cell anaemia is an X-linked recessive gene disorder.
Which of the following most appropriately describes haemophilia? (NEET 2016 Phase 1)
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