Question: 136: 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 :
(1) 47 chromosomes with XXY sex chromosomes
(2) 45 chromosomes with XO sex chromosomes
(3) 47 chromosomes with XYY sex chromosomes
(4) Trisomy of chromosome 21
Answer: Option (4)
Explanation:
The features described such as small round head, furrowed tongue, partially open mouth, broad palm, and a characteristic single palmar crease are typical clinical features of Down syndrome.
Down syndrome is a chromosomal disorder caused due to the presence of an extra copy of chromosome 21.
This condition is known as trisomy 21, where the total number of chromosomes becomes
2n + 1 = 47.
Individuals with Down syndrome show retarded physical growth, delayed psychomotor development, and varying degrees of intellectual disability.
Option (1) represents Klinefelter syndrome with XXY sex chromosomes.
Option (2) represents Turner syndrome with XO sex chromosomes.
Option (3) represents XYY syndrome.
Therefore, the correct karyotype finding for the given individual is trisomy of chromosome 21.