5.2 DNA Replication (CQ - exam)

Question 1

main objective of DNA replication?

Answer 1

Producing 2 identical DNA molecules from an original parental DNA molecule

Question 2

Why is DNA replication important for cell reproduction?

Answer 2

DNA replication is important in cell reproduction because without being able to produce DNA for newly created cells would make them useless

Question 3

Why is it important for newly replIcated daughter strands of DNA to have the same information as the parent strands?

Answer 3

It is important for replicated daughter strands have the same information as the parent strands because DNA replication’s main function is for cell growth and repair. Without the same transfer of the same information, then the cells would be unable to repair or grow.

Question 4

three basic phases of DNA replication.

Answer 4

1. Initiation: portion of the DNA double helix is unwound to expose the bases for new base pairing.
   - Replication begins at a nucleotide sequence, the origin of replication
   - Helicase unwinds the strand
   - SSBPs stabilizes the unwound single strands by preventing them from reforming hydrogen bonds
   - Topoisomerase relieves the the strain occurring during the unwinding
2. Elongation: 2 new strands of DNA are assembled
3. Termination: 2 new strands separate and the replication machine is dismantled

Question 5

Why does elongation take place in a slightly different way on each DNA strand? Explain how the leading and lagging strands of DNA molecule are replicated.

Answer 5

The elongation takes place in a slightly different way on each DNA strand because on the leading strand DNA is replicated continuously and the lagging strand discontinuously with Okazaki fragments. Therefore, each method of elongation is different on each DNA strand.

Question 6

Why does DNA replication require numerous enzymes?

Answer 6

Enzymes are essential to the DNA replication process due to its functionality to unwinding the DNA, synthesizing, stabilizing, relieving strain, etc. Each enzyme has its distinct function, one enzyme would be unable to possess all of these abilities due to shape and coding factors.

Question 7

one way that errors in replication are corrected.

Answer 7

DNA Polymerase II in the case of an incorrect base will add the correct base by using the parent strand as a template.

Question 8

What is the difference between a replication bubble and a replication fork? Write a short description of each.

Answer 8

Replication bubble is an area formed by the separating of DNA in both directions. These replication bubbles will eventually merge to form 2 complete strands

Replication fork is the point of separation of the 2 parent DNA strands. Eukaryotic cells have multiple of these sites. Prokaryotic cells have only one.

Question 9

Why is an RNA primer necessary for DNA replication?

Answer 9

RNA primers are attached by the primase because DNA polymerases need a double stranded region of the DNA to mimic for the rest of the strand.

Question 10

How are the three different DNA polymerase enzymes involved in both DNA replication and DNA repair?

Answer 10

DNA polymerase proofreads the new DNA strand after the nucleotides are added and removes RNA primers.
DNA polymerase II corrects the bases found to be incorrect.
DNA polymerase III adds nucleotides to the 3’ end.

Question 11

What is the importance of complementary base pairing in the structure of DNA?

Answer 11

Complementary base pairing is important in the structure of DNA because it allows bases to pair up with each other in a consistent way that betters the chances of accurately replicated DNA.

Question 12

Why are multiple origins of replication advantageous?

Answer 12

Multiple origins of replication is advantageous because they can be used in case of poor growing conditions or when the replication fork is having difficulties.

Question 13

DNA replication traits unique to eukaryotes

Answer 13

• 40 nucleotides added per second
• 15 DNA polymerases identified
• larger linear chromosomes
• 1000s origins of replication

Question 14

DNA replication traits unique to prokaryotes

Answer 14

• 1000 nucleotide per second
• 5 DNA polymerase identified
• smaller circular chromosomes
• 1 origin of replication

Question 15

DNA replication traits both eukaryotes and prokaryotes have

Answer 15

• requires origin of replication
• DNA strand elongation occur in 5’ to 3’ direction
• leading strand is continuous, lagging strand is discontinuous
• requires RNA primer for synthesis of okazaki fragments in the synthesis of lagging strand
• uses DNA polymerase enzymes

Question 16

Why are telomeres present at the ends of eukaryotic chromosomes?

Answer 16

they protect DNA from losing coding sequences during replication.

Question 17

“Telomeres are like cellular clocks:’ Explain what this statement means.

Answer 17

Cell senescence is a period of decline where coding regions of DNA are lost. Telomeres are connected to our aging and cell senescence occurs when there is no more telomeres left. Loss of DNA can induce cell death.