Chapter 11- DNA Replication

Question 1

What is the correct model of DNA replication?

Answer 1

semiconservative model

Question 2

Describe the semiconservative model

Answer 2

replicated DNA will have one old and one new strand of DNA

Question 3

Describe the conservative model

Answer 3

the two parent strands rejoin

Question 4

Describe the dispersive model

Answer 4

each strand is a mix of old and new

Question 5

Describe origins of replication

Answer 5

where the two DNA strands are separated forming a “bubble”.

Question 6

Describe the replication fork

Answer 6

the ends of the bubble where new DNA strands begin elongating.

Question 7

Bacterial DNA is what shape?

Answer 7

circular

Question 8

Describe helicases

Answer 8

enzymes that untwist the double helix at the replication forks

Question 9

Describe topoisomerase

Answer 9

goes ahead of replication forks, cuts, unwinds, and rejoins DNA strands

Question 10

Why is topoisomerase needed?

Answer 10

to keep the DNA strands from being too twisted

Question 11

Describe single-strand binding protein

Answer 11

holds the DNA strand straight so it can be used as a template

Question 12

What is a primer

Answer 12

a short strand of RNA that is laid down at the origin of replication

Question 13

What is primase?

Answer 13

enzyme that lays down the primer

Question 14

Describe DNA Polymerase III

Answer 14

adds DNA nucleotides to the 3’ end of the primer

Question 15

The new strands grow in ________ directions.

Answer 15

opposite

Question 16

DNA polymerases add nucleotides only to the __ ___of a strand

Answer 16

3’ end

Question 17

a new DNA strand can elongate only in the __ to __ direction

Answer 17

5’ to 3’

Question 18

Leading strand grows _______the origin of replication

Answer 18

in front of

Question 19

Lagging strand grows _______ of the origin of replication

Answer 19

behind

Question 20

Describe Okazaki fragments

Answer 20

a series of primers and new DNA segments

Question 21

Describe DNA polymerase I

Answer 21

removes the RNA primers and replaces them with DNA nucleotides

Question 22

Describe DNA ligase

Answer 22

connects the new DNA nucleotides

Question 23

___ ___________ proofread DNA as it is added

Answer 23

DNA Polymerases

Question 24

________ can repair __________ based pairs or ________ DNA

Answer 24

enzymes; mismatched; damaged

Question 25

Describe nucleotide excision repair.

Answer 25

cutting out damaged DNA and replacing it with new DNA

Question 26

Describe nuclease

Answer 26

an enzyme that cuts out damaged DNA

Question 27

In nucleotide excision repair, what happens after DNA is cut out?

Answer 27

1. DNA Polymerase adds new nucleotides2. Ligase seals the new nucleotides

Question 28

Why is DNA cut short after every replication?

Answer 28

DNA can’t be added to 5’ end new strands

Question 29

How is DNA code protected from being cut?

Answer 29

meaningless code protects the real code

Question 30

Describe telomeres

Answer 30

repetitive nucleotide sequences at the end of DNA that do not contain genes

Question 31

Describe telomerase

Answer 31

an enzyme that lengthens telomeres in gamete DNA

Question 32

Why is telomerase needed?

Answer 32

so a zygote can start off with a full set of telomeres

Question 33

If DNA replicated following the conservative model, what would the results of the Meselon-Stahl experiment look like?

Answer 33

There would be one 14N strand and one 15N strand

Question 34

If DNA replicated following the dispersive model, what would the results of the Meselon-Stahl experiment look like?

Answer 34

Each band would be a mix of 15N and 14N

Question 35

In prokaryotes, DNA replication is ___________ rather than ____________ (think direction)

Answer 35

bidrectional; unidirectional

Question 36

In prokaryotes, DNA replication begins at a specific origin site called a _______.

Answer 36

replicon

Question 37

DNA polymerase _, _, _, _ all repair damaged DNA.

Answer 37

I, II, IV, V

Question 38

DNA polymerase _, _, _ have 5'-3' polymerization and 3' to 5' exonuclease activity

Answer 38

I, II, III

Question 39

3' to 5' exonuclease does what?

Answer 39

Proof-read synthesized base pairs

Question 40

DNA polymerase _ has 5'-3' exonuclease activity

Answer 40

1

Question 41

What are the 3 helicase proteins in prokaryotic DNA?

Answer 41

Dna A, B, and C

Question 42

Describe DnaA

Answer 42

proteins responsible for initial steps in unwinding the helix

Question 43

Describe DnaB and DnaC

Answer 43

further opens and destabilizes the helix

Question 44

What specific type of topoisomerase reduces supercoiling?

Answer 44

DNA gyrase

Question 45

DNA polymerase III requires a primer with a free _ ________ ______.

Answer 45

3' hydroxyl group

Question 46

Describe concurrent sythesis

Answer 46

Both DNA strands are synthesized concurrently by looping the lagging strand to invert the physical but not biological direction of synthesis

Question 47

How do polymerases proofread DNA? (what do they look for)

Answer 47

They read the amount of methylation on each strand of DNA

Question 48

Compare eukaryotic and prokaryotic chromosome and DNA structure.

Answer 48

Eukaryotic chromosomes are linear and the DNA is complexed with proteins

Question 49

___ _ and ___ _ are the major forms of the enzymes included in initiation and elongation.

Answer 49

Pol α (little Alpha); δ (little Delta)

Question 50

Describe Pol α's and δ 's functions in synthesis.

Answer 50

Pol α synthesizes RNA primers during initiation on the leading and lagging strands. Polymerase switching occurs, and Pol α is replaced by δ for elongation

Question 51

Describe telomeres' function.

Answer 51

They form hairpin loops to make chromosomes appear inert

Question 52

Why are telomeres important?

Answer 52

They prevent recombination

Question 53

Why is lagging synthesis at the end of the chromosome a problem?

Answer 53

Once RNA primer is removed, there is no free 3' hydroxyl group from which to elongate

Question 54

What does telomerase do?

Answer 54

Direct synthesis of the telomere repeat sequence to fill the gap

Question 55

Describe the structure of telemoerse

Answer 55

A ribonucleotide protein with a RNA that serves as the template for the synthesis of its DNA compliment.