In the $lac$ operon system,the $lac$ gene-$I$ codes for:

During $DNA$ transcription,$mRNA$ is usually single-stranded. However,sometimes an $RNA$ molecule is produced that is complementary to the $mRNA$. This is called ...... and its function is to ...... .

The one gene-one enzyme hypothesis was postulated by

Genes that are involved in turning on or off the transcription of a set of structural genes are called:

In which of the following are monocistronic genes found?

What does '$4$' represent in the given figure?