Edward's syndrome, Patau's syndrome and Down's syndrome are due to

One of the following is sex-influenced character

In a gene pool, along with beneficial mutations those mutations also exists which are damaging to an individual. It has been found that these mutations are irreversible because

$I.$ they have survival value

$II.$ they are acquired

$III.$ they are recessive and carried by heterozygous individuals only

$IV.$ they show genetic drift

Choose the incorrect option for given statement

Cystic fibrosis, Myotonic dystrophy and Thalassemia are

Based on Lyon’s hypothesis, what will be the number of Barr bodies found in a human female suffering from Down’s syndrome