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?

Chemically,$DNA$ differs from $RNA$ in having:

The clover leaf model of $tRNA$ consists of:

Given below are two statements:
Statement $I$: Transfer $\text{RNAs}$ and ribosomal $\text{RNA}$ do not interact with $\text{mRNA}$.
Statement $II$: $\text{RNA}$ interference $\text{(RNAi)}$ takes place in all eukaryotic organisms as a method of cellular defence.
In the light of the above statements,choose the most appropriate answer from the options given below.

What are informosomes?

Briefly describe the following:
$(a)$ Transcription
$(b)$ Polymorphism
$(c)$ Translation
$(d)$ Bioinformatics