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
Who has putforth Mendel's conclusions in the form of laws
The character that is expressed in the $F_{1}$-generation is called the
Number of autosomal chromosomes in Drosophila
Assertion : Persons suffering from haemophilia fail to produce blood clotting factor $VIII$.
Reason : Prothrombin producing platelets in such persons are found in very low concentration.
In phenylketonuria