Pakistan MCQs

Mixture components retain much of their individual identity.
They can often be separated by physical methods.

Hydrogen bonds join bases across the two DNA strands.
Covalent phosphodiester bonds form each strand's backbone.

Ribosomes read mRNA codons.
TRNAs deliver corresponding amino acids.

Phosphodiester bonds connect the sugar of one nucleotide to the phosphate of the next.
They form the sugar-phosphate backbone.

One strand runs 5′ to 3′ and the other 3′ to 5′.
This orientation is important for replication enzymes.

DNA replication occurs before cell division.
Each daughter DNA molecule contains one old and one new strand.

The parental strands separate and serve as templates.
Each completed double helix preserves one original strand.

Helicase breaks hydrogen bonds between base pairs.
It opens the replication fork.

DNA polymerase extends a new strand using a template.
It adds nucleotides in the 5′ to 3′ direction.

Ligase seals breaks in the sugar-phosphate backbone.
It creates a continuous lagging strand.

DNA polymerase can follow the fork continuously on the leading template.
Synthesis still proceeds 5′ to 3′.

Its template orientation requires repeated short segments.
Ligase later joins these fragments.