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4.Principles of Inheritance and Variation
normal
$21$ trisomy in humans causes
A
Klinefelter's syndrome
B
Down's syndrome
C
Turner's syndrome
D
Patau's syndrome
Solution
| Disorders | Autosomal/Sex Linked | Symptoms | Effects |
| Down's syndrome | Autosomal aneuploidy $($trisomy, $+21)$ | Mongolian eyefold (epicanthus), open mouth, protruded tongue, projected lower lip, many loops on finger tip, palm crease | Retarded mental development $IQ\, ($below $40)$ |
| Turner's syndrome |
Sex chromosomal monosomy $44$ $+ XO$ |
Short stature females $\left( < 5^{\prime}\right)$ webbed neck, body hair absent menstrual cycle absent. sparse pubic hair, underdeveloped breasts narrow lips puffy fingers $ < $ span $ > \left\langle/ 5^{\prime}\right),>$ |
Sterile hearing problem |
| Klinefelter's syndrome |
Sexchromosomal aneuploidy (tri/tetrasomy of $X$ chromosome) $44+ XXY$ $44+ XXXY$ |
The males are tall with long legs, testes small, sparse body hair, Barr body present, breast enlargement | Gynaecomasti a azospermia sterile |
Standard 12
Biology
