DNA Replication

Question 1

What is the structure of DNA?

Answer 1

A phosphate group, hydroxyl on 3’C, base

Question 2

What is the structure of DNA’s backbone?

Answer 2

sugar, phosphate repeating

Question 3

What was the Hershey-Chase experiment?

Answer 3

Deciding if proteins or DNA is the genetic material. They used E. coli and labeled protein coats with sulfur and DNA with phosphorus and tagged them with radioactive material.

Question 4

What is copied and what does the copying in DNA replication?

Answer 4

DNA is copied and enzymes do the copying.

Question 5

What are the three stages of DNA replication?

Answer 5

1. ) Initiation: replication begins
2. ) Elongation: new strands of DNA are synthesized by DNA polymerase
3. ) Termination: replication ends

Question 6

What is the origin of replication initiation (ORI)?

Answer 6

replication bubbles: genetic sequences in DNA meant to unzip (replicates 5’ to 3’)

Question 7

What are the two steps in the process of DNA replication?

Answer 7

1. ) RNA polymerase adds an RNA primer to start DNA replication
2. ) DNA polymerase matches existing DNA bases with complementary nucleotides and links them

Question 8

What does DNA ligase do?

Answer 8

seals broken phosphodiester bonds using ATP to activate the 5’ end, then the new bond is formed

Question 9

What are the four steps of DNA synthesis?

Answer 9

1. ) RNA primase lays down an RNA primer
2. ) DNA polymerase extends RNA primer
3. ) A different DNA polymerase removes the primer and replaces it with DNA
4. ) DNA ligase forms a new bond joining the two DNA fragments

Question 10

Leading vs. lagging strand

Answer 10

leading strand: synthesized continuously from an initial primer
lagging strand: synthesized discontinuously with multiple priming events

Question 11

Lagging strand synthesis

Answer 11

1. ) RNA primer made by primate for each Okazaki fragment
2. ) discontinuous synthesis- DNA polymerase III
3. ) All RNA primers removed and replaced by DNA (DNA polymerase I)
4. ) backbone sealed by DNA ligase

Question 12

Unwinding DNA causes torsional strain

Answer 12

Helicases: use ATP to unwind DNA
Single strand binding proteins: coat single stranded DNA to keep them apart
Topoisomerase: prevent supercoiling

Question 13

Why does replication require a DNA clamp and loader?

Answer 13

Because DNA polymerase synthesizes only a short sting of nucleotides before falling off the template

Question 14

Sliding clamp

Answer 14

needed to synthesize long DNA strands, keeps polymerase on DNA strand until it runs into dsDNA, requires ATP hydrolysis

Question 15

Clamp loader

Answer 15

hydrolyzes ATP as it loads the clamp on to a primer-template junction

Question 16

Replisome

Answer 16

enzymes involved in DNA replication form a macromolecular assembly called the replisome. There are 2 replisomes per replication bubble

Question 17

Telomeres

Answer 17

• protect ends of chromosomes and maintain linear shape of chromosomes
• with each round of cell division, there is a gradual shortening of chromosomes because the last section of the lagging strand is unable to be replicated

Question 18

Telomerase

Answer 18

the enzyme that elongates the telomere of lagging strand using an internal RNA template

Question 19

PCR (polymerase chain rxn)

Answer 19

makes a copy of an existing DNA strand if there’s a primer. It’s used to amplify DNA and uses high temps to split DNA instead of helicase