Which of the following is a correct match?
Correct answer: A. Down's syndrome - 21st chromosome
- A. Down's syndrome - 21st chromosome
- B. Sickle cell anaemia - X chromosome
- C. Haemophilia - Y chromosome
- D. Parkinson's disease - X and Y chromosome
Explanation
The correct answer is Option A: Down's syndrome is caused by the presence of an extra copy of chromosome 21, known as trisomy 21. This genetic condition is characterized by a distinct facial appearance, developmental delays, and may include thyroid or heart disease.Option B is incorrect because sickle cell anaemia is not a sex-linked disorder; it is an autosomal disorder linked to chromosome 11.Option C is incorrect as haemophilia is caused by a mutation on the X chromosome, not the Y chromosome.Option D is incorrect because Parkinson's disease is not a hereditary condition linked to the X or Y chromosome; it is a complex disorder with both genetic and environmental factors.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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