Explain the mechanism of DNA replication with the help of a replication fork. What role does the enzyme DNA-ligase play in a DNA replication fork ?

OR

Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA.
 

DNA replication starts from a specific site called origin of recognition. (ORI)

For long DNA molecules, since the two strands of DNA cannot be separated in its entire length (due to very high energy requirement), the replication occur within a small opening of the DNA helix, referred to as replication fork. The DNA-dependent DNA
polymerases catalyse polymerisation only in one direction, that is 5'$\to$3' . This creates some additional complications at the replicating fork. Consequently, on one strand (the template with polarity 3'$\to$5' ), the replication is continuous, while on the other (the template with polarity 5'$\to$3' ), it is discontinuous. 

The discontinuously synthesised fragments are later joined by the enzyme DNA ligase.

OR

5’ A U G C A U G C A U G C 3’ Sense strand in RNA

3’ U A C G U A C G U A C G 5’ Anti-sense strand in RNA

The process of the formation of RNA from DNA is transcription.

The enzyme used is DNA dependent RNA polymerase.