Question 1

Origins are replication are ـــــــــــــــــــــ.

Accepted Answer

Origins of replication are typically AT-rich, meaning they have a higher proportion of adenine and thymine nucleotides than guanine and cytosine. This is because AT base pairs have only two hydrogen bonds, which are easier to break during replication than the three hydrogen bonds in GC base pairs. The AT-richness of origins makes them more accessible to replication machinery and easier to unzip at the start of DNA replication.

Question 2

All DNA replication results in two copies of double-stranded DNA,each copy having a parent strand and a newly synthesized strand.This is referred to asـــــــــــــــــــ .

Accepted Answer

Semi-conservative replication refers to the fact that one parent strand of DNA is conserved in each of the two daughter strands. This means that each new DNA molecule consists of one strand from the original molecule and one newly synthesized strand. This has been demonstrated experimentally by the use of isotopes and autoradiography. The other options, conservative replication, antiparallelism, and complementarity, are all important concepts in DNA replication, but do not specifically refer to the production of two identical copies of DNA.

Question 3

Replication is initiated at ـــــــــــــــــــ.

Accepted Answer

Replication is initiated at specific sites called origins of replication, which are located along the DNA molecules. These origins are known to be the starting points for the replication machinery to begin copying the DNA strands. Telomeres, centromeres, and the start of every gene are not locations where replication is initiated.

Question 4

DNA is duplicated during mitosis.

Accepted Answer

DNA is duplicated during the S phase of interphase, not during mitosis. Mitosis is the process of cell division that follows DNA replication.

Question 5

During which phase of the cell cycle is DNA replicated?

Accepted Answer

DNA replication occurs during the S-phase of the cell cycle. This is the phase where the cell duplicates its DNA in preparation for cell division.

Question 6

In replication,ــــــــــــــــــــــis responsible for opening up and unwinding the DNA at the origin.

Accepted Answer

Helicase is responsible for opening up and unwinding the DNA at the origin in replication. DNA polymerase adds nucleotides to the newly synthesized strand, ligase seals any gaps in the backbone of the DNA, and primase synthesizes an RNA primer for DNA polymerase to start replication. So, options A, B, and D are not the correct choices for the given question.

Question 7

During replicating,incoming nucleotides are always added to the free ــــــــــــــــof the preceding nucleotide.

Accepted Answer

During DNA replication, incoming nucleotides are always added to the 3' end of the preceding nucleotide, which has a free 3' hydroxyl group. This forms a phosphodiester bond between the 3' carbon of the sugar of the previous nucleotide and the 5' phosphate of the incoming nucleotide. Therefore, the correct choice is option C, which describes the free 3' hydroxyl group.

Question 8

Replication always proceeds ـــــــــــــــــــــــrelative to the new strand.

Accepted Answer

Replication always proceeds in the 5' to 3' direction relative to the new strand, known as the leading strand. DNA replication occurs bidirectionally from the origin of replication, but the lagging strand is synthesized in the opposite direction in short, discontinuous fragments called Okazaki fragments. Therefore, choice A and B are incorrect. The 3' to 5' direction is used by DNA polymerases to proofread and repair errors in the new strand, but it is not the direction of replication. Therefore, choice C is also incorrect.

Question 9

The process ofــــــــــــــــــــــــــ does not use mitosis.

Accepted Answer

Gamete formation involves meiosis, not mitosis, to produce haploid cells from diploid ones, ensuring genetic diversity and the correct number of chromosomes in sexual reproduction.

Question 10

How many origins are replication are typical of bacterial circular chromosomes?

Accepted Answer

Bacterial circular chromosomes typically have a single origin of replication from which DNA replication proceeds bidirectionally.

Question 11

G1,S,and G2 are collectively calledـــــــــــــــــــ .

Accepted Answer

G1, S, and G2 phases make up interphase, which is the period of the cell cycle during which the cell prepares for division by growing and replicating its DNA.

Quiz 10: Cell Division and DNA Replication