The clover leaf model of $tRNA$ consists of:

Which of the following is not a correct statement?

Western blotting is used for the identification of .....

$A$ complete set of chromosomes or cell genes inherited as a unit from a parent is known as

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

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?