2022 Phase 2 Principles of Inheritance and VariationChromosomal Disorders – Down's Syndrome Easy Question 2 of 3 in Chromosomal Disorders – Down's Syndrome

If a female individual is with small round head, furrowed tongue, partially open mouth and broad palm with characteristic palm crease. Also the physical, psychomotor and mental development is retarded. The karyotype analysis of such an individual will show

A Trisomy of chromosome 21
B 47 chromosomes with XXY sex chromosomes
C 45 chromosomes with XO sex chromosomes
D 47 Chromosomes with XYY sex chromosomes

The answer is A.

Solution

These are features of Down's syndrome, caused by the presence of an additional copy of chromosome 21 (trisomy 21, 2n + 1). This aneuploidy results from non-disjunction during gamete formation.

Concept Chromosomal disorders - Down's syndrome

Chromosomal Disorders – Down's Syndrome in past papers

3 questions from this chapter have appeared across 3 exam years.