The first restriction enzyme to be isolated and characterised was

$A$ - Restriction endonucleases are also called 'molecular scissors'.
$R$ - When fragments generated by restriction endonucleases are mixed,they join together due to their sticky ends.

Restriction enzymes that are used in the construction of recombinant $DNA$ are endonucleases which cut the $DNA$ at 'specific-recognition sequence'. What would be the disadvantage if they do not cut the $DNA$ at specific-recognition sequence?

Which enzyme is used to join the ends of two strands of nucleic acid?

The $DNA$ used as a carrier for transferring a fragment of foreign $DNA$ into a suitable host is called

Match the following columns:

Column-$I$	Column-$II$
$(a) \ Cla \ I$	$(1) \ \text{Antibiotic resistance gene}$
$(b) \ pBR322$	$(2) \ \text{Origin of replication}$
$(c) \ tet^R$	$(3) \ \text{Restriction enzyme}$
$(d) \ ori$	$(4) \ \text{Plasmid}$