What do genes control?

Which of the following is $NOT$ associated with the study of genetics?

After a mutation at a genetic locus,the character of an organism changes due to the change in:

Base substitution caused by base analogs is known as:

Mark the correct match.

Read the following four statements ($1$ to $4$):
$1$. In transcription,uracil pairs with adenosine.
$2$. Regulation of $lac$ operon by a repressor is referred to as positive regulation.
$3$. The human genome contains approximately $50,000$ genes.
$4$. Haemophilia is a sex-linked recessive disease.
How many of the above statements are correct?