Question

What diseases are caused by chromosomal abnormalities?

Answer 1

Genetic disorders are defects that are caused by a genetic mechanism like mendelian genes, multi factor genes, chromosomal aberrations and abnormalities. The genetic disorders caused by chromosomal aberrations and abnormalities are known as chromosomal disorders. The chromosomal abnormalities develop due to defective synapsis and disjunction during meiosis.

Complete answer:
Diseases, caused by chromosomal abnormalities are:
Down’s Syndrome: Due to trisomy of chromosome 21. Caused by an occasional non-disjunction during meiosis when a gamete comes to possess an extra chromosome (n+1). Fusion with a normal gamete [n+ (n + 1)] produces trisomy. They have short stature, small round heads, small ears, open mouth, projecting lower lip, protruding furrowed tongue, short flat nose, short neck, short broad hands.
Klinefelter’s Syndrome (44+XXY/XXXY): The individuals are phenotypically male. The defect appears due to fusion of egg having unreduced sex complement (A + XX) with normal androsperm (A+Y) or sperm with unreduced sex complement (A + XY) and a normal (A + X) or abnormal egg (A + XX). Effects are long legs, sparse body hair, small prostate gland, small testes, azoospermia, enlarged breasts in more than 50% of the cases.
Turner’s Syndrome (44+XO): The individuals are phenotypically female. The effect appears due to fusion of a gamete without sex chromosome (A+O) and a gamete with one X-chromosome (A+X), i.e., between deficient egg and gynosperm or normal egg and deficient sperm. Individuals have short stature, webbed neck, low posterior hair-line, increased carrying angle of elbow, . limited secondary sex characters.
Edward’s syndrome: Due to trisomy of chromosome 18. Effects are Long but narrow skull, small face, low set ears, short digits, webbed neck, corneal opacity, mental retardation.
Cri du chat: Short arm of chromosome 5 is deleted. Microcephaly, increased distance between eyes, moon face, cat-like cry of neonate.

Note:
Chromosomal disorders may or may not be transmitted. The disorders can be known through amniocentesis. Some other chromosomal disorders are : Patau’s syndrome (Due to trisomy of chromosome 13), Wolf Hirschhorn syndrome (deletion in short arm of chromosome 4), Nooman’s syndrome (male Turner’s syndrome).