DNA & The Gene

Question 1

How many chromosomes does each somatic cell in your body have?

Answer 1

46

Question 2

What is the name of the specific sites at which DNA replication begins?

Answer 2

Origins of replication

Question 3

How many origins of replication do bacterial chromosomes have?

Answer 3

1

Question 4

True/False: Eukaryotes have multiple origins of replication.

Answer 4

True

Question 5

True/False: DNA replication proceeds in only one direction from the origin?

Answer 5

False, both directions

Question 6

What untwists the double helix and separates the strands of DNA?

Answer 6

Helicase

Question 7

What binds to separated DNA strands to prevent repairing?

Answer 7

Single-strand DNA binding proteins (SSBPs)

Question 8

What relieves strain ahead of replication fork caused by unwinding by breaking, swiveling, and rejoining DNA strands?

Answer 8

Topoisomerase

Question 9

Can enzymes that synthesize DNA start a new chain?

Answer 9

No, they can only add to an existing strand. (need an OH group)

Question 10

What does primase do?

Answer 10

Lays down an RNA primer that is complementary to the template strand.

Question 11

What are DNA polymerases?

Answer 11

enzymes that catalyze the synthesis of DNA by adding nucleotides to an existing chain.

Question 12

What direction do DNA polymerases add dNTPs?

Answer 12

Only in the 5’ to 3’ direction

Question 13

What adds a nucleotide to the RNA primer and then keeps adding complementary nucleotides to the growing strand?

Answer 13

DNA polymerase III

Question 14

How is the leading strand synthesized?

Answer 14

Towards the replication fork

Question 15

How many primers does the leading strand require?

Answer 15

1

Question 16

How often is the leading strand synthesized?

Answer 16

Occurs continuously

Question 17

How is the lagging strand synthesized?

Answer 17

Away from the replication fork

Question 18

Why is the lagging strand discontinuous?

Answer 18

New fragment cannot be started until the fork moves forward and exposes the template

Question 19

What is the name of the fragments created by the lagging strand?

Answer 19

Okazaki fragments

Question 20

What does DNA polymerase I do?

Answer 20

Replaces the RNA primer with DNA nucleotides

Question 21

What does DNA ligase do?

Answer 21

Joins all of the fragments into a continuous strand.

Question 22

What is the name of the macromolecular machine formed by the enzymes involved in replication?

Answer 22

Replisome

Question 23

What is active during embryonic development, but shuts off in most somatic cells at a later stage?

Answer 23

Telomerase

Question 24

What is telomerase composed of?

Answer 24

Protein and RNA

Question 25

Proofreading and Repair slide

Answer 25

Look at the slide

Question 26

What is it called when other enzymes remove and replace incorrectly paired nucleotides?

Answer 26

Mismatch repair (MMR)

Question 27

Defects in the enzymes responsible for MMR can lead to what?

Answer 27

Cancer

Question 28

What is it called when a damaged segment is cut out by a nuclease and the gap is filled in by DNA polymerase and ligase using the damaged strand as a template?

Answer 28

Nucleotide Excision repair (NER)

Question 29

What would be an example of NER (nucleotide excision repair)?

Answer 29

Damage from UV light