Question

Genotype of Down’s syndrome is
A) 45 + XX
B) 44 + XY
C) 44 + XXY
D) 22 + XY

Answer 1

Hint: The genotype is Trisomy 21 for Down syndrome. When there has been a non-jusduction in the chromosome in meiosis, it is induced.

Complete answer:
First we should know about Down’s syndrome to answer this question. Down syndrome ( DS) is a significant cause of congenital heart disease and mental retardation. DS is concerned with congenital gastrointestinal tract abnormalities, an elevated risk of tumours, immune system deficiencies, and Alzheimer's-like dementia, in addition to a distinctive range of facial and physical traits.

Now, let us find the solution from the options-
> Down syndrome is a chromosomal disorder defined by the existence of an additional copy of genetic material on chromosome 21, either in whole (trisomy 21) or in part (like due to translocations). The > Down syndrome is referred to as trisomy 21 and is described as 45+XX or 45 + XY.
Down syndrome does not show 44 + XY. As the 44XY means two chromosomes are absent and that shows the organism exhibits abnormalities. Thus, the option B is incorrect.
> Depending on the number of X-chromosomes, a human male with Klinefelter’s syndrome, 44+XXY/ 44+XXXXY/ 44+XXXY can have 1, 2 or 3 Barr bodies. The presence of an additional X-chromosome copy generates some feminine characters in male individuals. They are pure feminised males (Gynecomastia) with swollen breasts. Thus, the option C is incorrect.
> Down syndrome does not show 22 +XY genotype because the genotype of down syndrome is trisomy 21. Thus, the option D is incorrect.

Thus, the correct answer is option A 45 + XX.

Note: The number of sex chromosomes in Down's syndrome is normal because it is an autosomal aneuploid. Down's syndrome is an individual that is trisomic in the twenty first pair of chromosomes.