Question

One of the following is a mismatch.

• A. Down syndrome - Autosomal aneuploidy
• B. Klinefelter syndrome - XO complement
• C. Haemophilia - Sex linked
• D. Turner syndrome - Females with retarted sexual development

Answer 1

The correct option is B Klinefelter syndrome - XO complement

• Aneuploidy is the presence of one or more extra chromosomes in an organism. Down syndrome is trisomy-21, i.e., presence of chromosome 21 in three copies. It is an autosomal aneuploidy and does not affect any sexual characters.
• The presence of one or more extra copy of X-chromosome in males causes Klinefelter syndrome. The affected individual has a 44+ XXY chromosome. The presence of an extra copy of the X-chromosome produces some feminine characters in otherwise male individuals.
• Turner syndrome is monosomy caused by the absence of one copy of the X-chromosome from females and is denoted by 44 +XO or 45, X. These females carry only a single copy of genes present on X-chromosomes and, hence, are sterile females with undeveloped breast.
• Haemophilia is X- linked disorder, the genes for which are present on the X-chromosome which is one of the sex chromosomes.

Hence, option B is mismatched.