Frequency of Down’s syndrome increases when the maternal age is
Above $35$ years
Below $35$ years
During $1^{st}$ pregnancy
In mothers of at least $3$ children
Barr bodies and drumsticks are of what significance to genetists and biologists
The diagrammatic representation of the chromosomes of an individual is called
A fruit fly is heterozygous for sex-linked genes when meted with normal female fruit fly, the males specific chromosome will enter egg cell in the proportion
Describe test cross. why it is necessary ?
Which one of the following mutation partially or fully reverses the harmful effects of previous mutation