The trisomy for 21st chromosome is called

Down's syndrome

Turner's syndrome

Sickle cell anaemia

Klinfelter's syndrome

Solution

Down's syndrome

Abnormality	Cause	Characteristic
Down's Syndrome	Trisomy of 21^st chromosome (45 A + XX/ XY)	Mental retardation, prominent head, flattened nasal bridge, open mouth, short stature etc
Turner's Syndrome	Non- disjunction of sex chromosome (2n = 45; 44A +XO)	Sterile female, webbed neck, no breast development, no menstruation or egg production
Klinefelter's Syndrome	Non- disjunction of sex chromosomes (2n = 47; 44A + XXY)	Sterile male with low IQ, testes underdeveloped.
Sickle cell anaemia	Molecular gene mutation of gene Hb^A	Sickle shaped RBCs, do not transport O₂ efficiently

Some More Questions From Principles of Inheritance and Variation Chapter

For Daily Free Study Material Join wiredfaculty