Question

DNA replication is known to follow which of the following patterns

Select one:

a. Conservative mechanism

b. Dispersive mechanism

c. Untraditional mechanism

d. Semi-conservative mechanism

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In the absence of DNA polymerase 1, a cell would be unable to

Select one:

a. Polymerize the Okazaki fragments

b. Remove the primers

c. Initiate telomerase activity

d. Synthetize DNA on the leading strand

e. Synthetize new DNA on both strands

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At the end of the DNA replication process, telomerase activity is higher

Select one:

a. At the 3’ end of the lagging strand

b. At the 3’ end of both strands

c. At the 3’ end of the leading strand

d. At the 5’ end of the lagging strand

e. At the 5’ end of the leading strand

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Which of the following is/are true about the two DNA strands that form a helix?

Select one:

a. The 2 strands are antiparallel and complementary to each other

b. The 2 strands are linked to each other by peptide bonds

c. In a gel electrophoresis, DNA would run toward the negative electrode

d. Answers A and C are correct

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Answer 1

1) The correct answer is d) Semi-conservative mechanism.

Reason : DNA replication is always of semi-conservative nature, because the resultant helix of daughter strands consists of one strand which is perfectly identical to one of the strands of parent helix. Hence it is semi-conservative, as only half of the parent helix is conserved in daughter helix.

2) The correct answer is b) Remove the primers.

Reason : The actual function of DNA Polymerase 1 is to remove the RNA primers from the strand, and then replacing them with DNA. RNA primers are hydrolysed by DNA polymerase 1, and then the remaining gaps are filled. Absence of DNA Polymerase 1 will prevent the removal of Primers.

3) The correct answer is c) At the 3’ end of the leading strand

Reason : Due to the improper and incomplete replication near Okazaki Fragments, DNA always gets shortened after each replication cycle. The 5'-3' (leading) strand will be completely synthesized but the 3'-5' (lagging) strand will always be shortened. So telomerase needs to bind near the 3' end of the leading strand, so that the complementary DNA (to fill the gaps) are added towards the usual 5' to 3' direction in the lagging strand.

4) The correct answer is a) The 2 strands are antiparallel and complementary to each other.

Reason : The two strands will always remain complementary to each other since A binds with T & vice versa and G binds with C & vice versa. Other combinations are not possible. The strands are anti parallel, with one in 5'-3' direction and the other one being in 3'-5' direction. They are linked to each other by Hydrogen bonds, and they always migrate towards positive electrode (since DNA is negatively charged).

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