Segment of $DNA$ which is responsible for inheritance and expression of a particular character is known as

One functional unit of a gene which specifies the synthesis of one polypeptide is known as:

Match the following:

Column-$I$	Column-$II$
$(1)$ Ligase	$(p)$ Segment of $DNA$
$(2)$ $RNA$ polymerase + Rho factor	$(q)$ Replication
$(3)$ $RNA$ polymerase	$(r)$ Termination
$(4)$ Cistron	$(s)$ Elongation

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.

Which of the following statements is incorrect?

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ $DNA$	$(P)$ Most abundant
$(2)$ $m-RNA$	$(Q)$ Various types based on anticodons
$(3)$ $t-RNA$	$(R)$ Carries information as genetic code
$(4)$ $r-RNA$	$(S)$ $A$ specific part acts as a template