In human female, barr bodies are formed by
Inactivation of mother's $X$ chromosome
Inactivation of father's $X$ chromosome
Inactivation of both mother's and father's $X$ chromosomes
Inactivation of either mother's or father's $X$ chromosome
$A$ : The heterozygotic female for haemophilia may transmit the disease to sons.
$R$ : Such traits show criss-cross inheritance
Chromosomes are made up of
Which one of the following is a dominant trait
Preformation theory concerning transmission of characters was given by
Brachydactyly is due to