In Operon concept, the regulator gene regulates chemical reactions in the cell by

How many of the given statements $(i-iv)$ is/are correct?

$i.$ In transcription, adenosine pairs with uracil.

$ii.$ Regulation of lac operon by repressor is referred to as positive regulation.

$iii.$ The human genome has approximately $50,000\; genes.$

$iv. $ Haemophilia is a sex-linked recessive disease.

In the lac operon, the structural genes are switched off when

Which of the following would you expect to find in an inducible system?

Operon is