$A$ gene which controls more than one character is called $:-$

Find the correct statement.
$(1)$ Generally a gene regulates a trait,but sometimes one gene has an effect on multiple traits.
$(2)$ The trait $AB$-blood group of man is regulated by one dominant allele and another recessive allele. Hence it is co-dominant.

The gene disorder phenylketonuria is an example of

The best example for pleiotropy is

In an organism,mutation in a single gene exhibits multiple phenotypic expressions. Identify the underlying genetic mechanism in the above instance.

$A$ pleiotropic gene