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 :
- Trisomy of chromosome 21
- 47 chromosomes with XXY sex chromosomes
- 45 chromosomes with XO sex chromosomes
- 47 chromosomes with XYY sex chromosomes
Answer
(1) Trisomy of chromosome 21
Solution
As per NCERT, Down's syndrome is caused by the presence of an additional copy of chromosome number 21 (trisomy of 21).
The affected individual is short statured with small round head, furrowed tongue and partially open mouth; the palm is broad with characteristic palm crease; physical, psychomotor and mental development is retarded.
XXY is Klinefelter's syndrome (male) and XO is Turner's syndrome, which do not show these features.
∴ The karyotype shows trisomy of chromosome 21.
Answer: (1)