Define aneuploidy. How is it different form polyploidy? Describe the individuals having following chromosomal abnormalities.
(a) Trisomy of 21st Chromosome
(b) XXY
(c ) XO

Explanation

Aneuploidy is a phenomenon which occurs due to non-disjuction, resulting in gain or loss of one or more chromosomers during meiosis.
Aneuploidy is different from polyploidy. Polyploidy is a phenomenon in which the organisms contain more than two monoploid valure or basic sets of chromosomes. i.e., -3n, 4netc. Example of such organisms are certain fish and salamanders and is commonly found in plants like grapes, banana.
Chromosomal Abnormalities
(a) Down's syndeome is an autosomal disorder that is caused by the trisomy of chromosome 21.
The individual is short statured with round head, open mouth, protruding tongue, short neck, slanting eyes, and broad short hands. The individual also shows reatrded mental and physical growth under developed gonads and genitats, etc.
(b) Klinefelter's syndrome is the chromosomal disorder that is caused by the presence of an additional copy of X-chromosome resultiong in the karyotype 45+XXY.
In this disorder sex of the individual is masculine but possess feminine characters also. The individual shows gynaecomastia i.e., development of breasts. The individual will be often sterile having poor beard growth and feminine pitched voice.
(c ) Turner's syndrome is the chromosomal disorder that is caused by the absence of one of the X-chromosomes, resulting in the karyotype 45+XO.
In this disorder the individual (female) will be sterile with rudimentary ovaries. Other symptoms include shield-shaped thorax, webbed neck, poor development of breasts, short stature, small uterus and puffy fingers.