Mule is an offspring of
Male and female donkey
Cow and ox
Male ass and mare
Male horse and female ass
Self sterility in "Nicotiana'' was reported by
Linked gene are separated by
The common point of attachment of all the arms of polytene chromosome, is known as
Down's syndrome occurs in the ........... pair of chromosome by increasing a chromosome.
The recessive genes located on $X$-chromosome in humans are always