Presence of a single allele of a character in a diploid organism is known as $:$

Match the columns:

Column $I$	Column $II$
$(a)$ Sickle cell anaemia	$(p)$ Homogentisic acid
$(b)$ Alkaptonuria	$(q)$ Lack of Melanin
$(c)$ Albinism	$(r)$ Accumulation of Amino acid
$(d)$ Phenylketonuria	$(s)$ Defective haemoglobin

Which of the following phenomena leads to variation in $DNA$?

Why did Mendel's work remain unrecognized for a long time?

Which of the following structures is identical in monozygotic twins?

The inheritance of $ABO$ blood group is an example of which of the following conditions?
$I -$ Complete dominance,$\quad II -$ Co-dominance
$III -$ Multiple allelism,$\quad IV -$ Incomplete dominance