By using the diagram,select the correct option for $X$ and $Y$.

'Central Dogma' was proposed 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.

$Escherichia \ coli$ is an important material for genetic experiments because

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

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?