Lyon hypothesis deals with

A distinct mechanism that usually involves a short segment of $DNA$ with remarkable capacity to move from one location in a chromosome to another is called

$A$ : The heterozygotic female for haemophilia may transmit the disease to sons.
$R$ : Such traits show criss-cross inheritance

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

Barr bodies are

Which of the following are most abundant types of antibodies