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IBH Biology

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Replication Of DNA

Question 1 of 12

1

Replication (of DNA) is quite separate from cell division and takes place in the interphase nucleus, well before the events of nuclear division. What enzyme unzips the DNA strands and holds them apart to allow the transcription process to occur?

Select one of the following:

  • Helicase

  • DNA polymerase

  • RNA polymerase

Explanation

Question 2 of 12

1

The strands of the DNA double helix are built up individually from free nucleotides, but before they can be condensed together the DNA double helix has to unwind, helicase does it's job and the two strands act as templates. Complementary base paring takes place and hydrogen bonds form. Finally the sugar and phosphate groups of adjacent nucleotides a condensed together and this is catalysed by which enzyme?

Select one of the following:

  • DNA polymerase

  • Helicase

  • DNA polymerase II

Explanation

Question 3 of 12

1

The two strands of each DNA molecule then wind up into a double helix and one strand of each new double helix comes from the parent chromosome and the other a newly synthesised strand. What is this arrangement known as?

Select one of the following:

  • Semi-conservative replication

  • Multi-conservative replication

  • Conservative replication

  • Recycling

Explanation

Question 4 of 12

1

What are the two roles of the enzyme DNA polymerase?

Select one or more of the following:

  • Unwinding the DNA double helix

  • Condensing sugar and phosophate groups of adjacent nucleotides

  • Proof-reading new strands

  • Forming hydrogen bonds between nucleotides

Explanation

Question 5 of 12

1

In eukaryotic chromosomes, replication is initiated at many points along the DNA double helix, called ___ . Here DNA replication always occurs in a ___ direction because the DNA polymerase that catalyses the condensation reaction (a.k.a ___ ) can only work in this direction.

Select one of the following:

  • a replication fork | 5' -> 3' | DNA polymerase III

  • a fork split | 5' -> 3' | DNA polymerase II

  • a replication fork | 3' -> 5' | DNA polymerase III

Explanation

Question 6 of 12

1

After the helicase has catalysed the uncoiling of the DNA double helix, the enzyme ___ adds a short RNA primer to the exposed strand and and to this ___ then adds succeeding free nucleotides by complementary base paring away from the direction of the advancing replication fork.

Select one of the following:

  • RNA primase | DNA polymerase III

  • RNA primase | DNA polymerase II

Explanation

Question 7 of 12

1

After the helicase has catalysed the uncoiling of the DNA double helix, the enzyme ___ adds a short RNA primer to the exposed strand and and to this ___ then adds succeeding free nucleotides by complementary base paring away from the direction of the advancing replication fork.

Select one of the following:

  • RNA primase | DNA polymerase III

  • RNA primase | DNA polymerase II

Explanation

Question 8 of 12

1

After the helicase has catalysed the uncoiling of the DNA double helix, the enzyme ___ adds a short RNA primer to the exposed strand and and to this ___ then adds succeeding free nucleotides by complementary base paring away from the direction of the advancing replication fork.

Select one of the following:

  • RNA primase | DNA polymerase III

  • RNA primase | DNA polymerase II

  • mRNA primase | RNA polymerase

Explanation

Question 9 of 12

1

Relatively short lengths of DNA are formed by this process, known as ___ . Later, the RNA primer between fragments is removed and replaced with DNA by ___ and then fragments are annealed into one continuous strand by ligase.

Select one of the following:

  • Okazaki fragments | DNA polymerase I

  • Ozakaki fragments | DNA polymerase II

  • Okazaki fragments | DNA polymerase III

Explanation

Question 10 of 12

1

Meanwhile on the exposed 5' -> 3' strand, ___ adds nucleotides by complementary base pairing to the free ___ end of the new strand in the same direction as the replication fork. This process occurs immediately behind the advancing helicase as fresh template is exposed.

Select one of the following:

  • DNA polymerase III | 3'

  • DNA polymerase III | 5'

  • DNA polymerase I | 3'

  • DNA polymerase I | 5'

Explanation

Question 11 of 12

1

The combination of a pentose sugar with a base is known as a nucleotide.

Select one of the following:

  • True
  • False

Explanation

Question 12 of 12

1

Nucleotides combined by the action of DNA polymerase are not in their monophosphate form, but are as nucleoside triphosphates . In each condensation reaction, two of the three phosphate groups are excluded.

Select one of the following:

  • True
  • False

Explanation

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