Question

Answer in 40 to 80 words:
Write the karyotype of the following syndromes:
A. Down’s syndrome
B. Klinefelter’s syndrome
C. Turner’s syndrome

Answer 1

Hint: Karyotype is the pictorial representation of the chromosomes of a person. It helps in determining any abnormality or mutation present in the chromosome of the person. Thus it is useful for the study of chromosomal disorders.

Complete answer:
Down’s syndrome
It is also called Mangolian Idiocy or Mongolism. It is due to trisomy of the 21st chromosome. The syndrome is characterized by rounded face, broad fore-head, small ears, flattened nasal bridge, open mouth, protecting lower lip, protruding tongue, vertical fold epicanthus on either side of nose, skin fold at ear corners, short neck, small flat hands with stubby little finger, loose jointedness at ankles, mental retardation, cardiac deformities, underdeveloped gonads and genitals.
Klinefelter’s syndrome
It was discovered by Klinefelter in 1942. The individual has a sex chromosomes XXY.
The individuals are males with underdeveloped testes, azoospermia, occurrence of barr body, feminine secondary sex characters or gynecomastia like very few body hairs and enlarged breasts, small prostate glands, long limbs and mental retardation. Individuals are sterile.
Turner’s syndrome
In this the individual has a single X-chromosome and the genotype is 44+XO due to the fusion of an ovum with genotype (22+0) with gymnosperm (22+X).
Individuals are sterile with rudimentary ovary and under-developed breasts and sparse pubic hairs.
All these are studied by karyotyping that involves the following steps- isolation, staining and examining of the chromosomes under the microscope.

Note: Humans have 23 pairs of chromosomes that include 22 pairs of autosomes and one pair of allosomes. Klinefelter’s syndrome, and Turner’s syndrome are disorders caused by abnormalities in sex chromosomes while Down’s syndrome is an autosomal disorder.