Question

1 pt 1 Question 1 Why must one strand of DNA be replicated in fragments? DNA polymerase can only add 20 nucleotides in a strand and then must start over ODNA polymerase can only add nucleotides to the 3 hydroxyl of a growing strand O it would be too crowded for two DNA polymerases to be going in the same direction all of the above Question 2 1 pt the DNA would spin and possibly break while being opened in the process of DNA If a cell were lacking replication O helicase primase topoisomerase ligase

Answer 1

1. The correct answer is b

Basically, DNA has 2 strands-the leading strand and the lagging strand. The leading strand is always synthesized continuosly in 5'-3' direction where nucleotides are added to 3' ends, whereas lagging strand in always synthesized in fragments. Because DNA polymerase cannot add nucleotides to 5' end, DNA strand is replicated in fragments because the DNA polymerase gets free 3'end to add nucleotides and replication can proceed in 5'-3' direction. Every time it is not possible for DNA polymerase to start its replication process from scratch and hence it uses the existing 3' end of the pre-existing strand to add nucleotides. These fragments are further sealed with the enzyme ligases.

2. The correct answer is c

Basically, helicase and topoisomerase function go hand in hand. Helicases unwind the two DNA strands by breaking the hydrogen bonds between the two strands whereas topoisomerase helps to relieves any tension that had been created by helicases while unwinding that is present by breaking the phosphodiester bond or linkage in the backbone. Helicase simply goes on unwinding and topoisomerase goes behind it to relieve the tension. If the cells lack topoisomerase, the tension created by helicase would not get released and this would lead to creating more tensions and ultimately DNA would break off.

Primase enzyme synthesizes short RNA sequences called the primer that are complementary to ssDNA (single stranded DNA). This are responsible to start the replication process by creating double complementary strands.

Ligase basically, acts as a DNA repairing mechanism where they function to seal the fragments between the strands and repair any damage caused to the DNA.