Question

Write a short note on chromosomal disorders.

Answer 1

Step 1: Understanding the Concept:
Chromosomal disorders result from an abnormal number of chromosomes (aneuploidy) or structural changes in chromosomes, and often produce characteristic sets of symptoms in affected individuals.

Step 2: Down's Syndrome:
Caused by trisomy of chromosome 21 (three copies instead of two). Features include short stature, a small round head, a partially open mouth with a protruding, furrowed tongue, and varying degrees of mental retardation.

Step 3: Klinefelter's Syndrome:
Caused by an extra X chromosome, karyotype 47, XXY. Affected individuals are male but show feminine body development (e.g. gynaecomastia) and are typically sterile.

Step 4: Turner's Syndrome:
Caused by the absence of one X chromosome in females, karyotype 45, X0. Features include short stature, a webbed neck, and sterility due to rudimentary, non-functional ovaries.

Final Answer:
\(\text{Chromosomal disorders (e.g. Down's, Klinefelter's, Turner's syndromes) arise from abnormal chromosome number or structure}\)