Molecular Genetics: DNA Replication

Question 1

semiconservative model

Answer 1

each double helix has one parent strand and one daughter stand

Question 2

conservative model

Answer 2

each newly synthesized helix has two daughter strands

Question 3

dispersive model

Answer 3

each strand in double helix has mixture of parent and daughter sections

Question 4

deoxyribonucleoside triphosphates (dNTPs)

Answer 4

nucleotide monomers for DNA synthesis - provide energy for exergonic DNA synthesis by cleaving off two phosphates

Question 5

what direction does DNA polymerase work

Answer 5

5’ to 3’

Question 6

DNA polymerases work by

Answer 6

adding dNTP to free 3’ OH group on an existing molecule

Question 7

DnaAproteins

Answer 7

bind to DnaAboxes to separate AT dense area - forms replication bubble

Question 8

leading strand

Answer 8

synthesized continuously in the same direction as the replication fork

Question 9

lagging strand

Answer 9

synthesized in Okizaki fragments away from the replication fork

Question 10

topoisomerase

Answer 10

relieves twisting forces on double helix as it unwinds

Question 11

helicase

Answer 11

unzips the double helix, responsible for moving replication fork

Question 12

single-stranded DNA-binding proteins

Answer 12

stabilize DNA strands to keep them separated during replication

Question 13

primase

Answer 13

synthesizes RNA primer to begin building a new strand of DNA

Question 14

sliding clamp

Answer 14

subunit that holds DNA polymerase onto DNA strand

Question 15

DNA polymerase III 5’ to 3’

Answer 15

adds dNTPs to new strand and during nucleotide excision repair

Question 16

DNA polymerase I

Answer 16

replaces RNA primers with DNA nucleotides during replication of the lagging strand

Question 17

DNA ligase

Answer 17

seals the backbone of DNA strand by forming phosphodiester bonds between the fragments

Question 18

replisome

Answer 18

all of the DNA replication enzymes working together

Question 19

Werner syndrome

Answer 19

mutation in WRN gene that codes for helicase - rapid aging after puberty

Question 20

why does the template strand in eukaryotes shorten with each replication?

Answer 20

there is a 3’ overhang on the template strand (for the lagging strand), eventually runs out of room to add an RNA primer

Question 21

telomeres

Answer 21

ends of linear chromosomes made of non-coding DNA repeats

Question 22

telomerase

Answer 22

protein with RNA template inside - maintains telomeres to prevent chromosome shortening

Question 23

telomerase uses reverse transcriptase activity

Answer 23

(RNA to DNA) RNA template inside binds with end of DNA, then adds dNTPs to extend the telomere

Question 24

Hayflick limit

Answer 24

number of times a cell can divide before cell death - correlates with telomere length

Question 25

telomerase expressed in

Answer 25

stem cells and gamete-producing cells

Question 26

positive and negative to telomerase expression in somatic cells

Answer 26

reduced signs of aging BUT increases chance of cancer (cells never reach Hayflick limit - tumor grows)

Question 27

DNA polymerase 3’ to 5’

Answer 27

exonuclease activity that proofreads and corrects base-pairing mistakes during replication

Question 28

mismatch repair after replication

Answer 28

proteins recognize misshapen helix and identifies template strand (more methylated) to excise and resynthesize the daughter strand

Question 29

mutagens

Answer 29

damage DNA which interferes with DNA replication which leads to increased risk of mutation

Question 30

nucleotide excision repair

Answer 30

recognition proteins identify damaged DNA - removed by nuclease - repaired by DNA polymerase III and DNA ligase

Question 31

Polymerase Chain Reaction

Answer 31

used to replicate and amplify a section of DNA in the lab

Question 32

Taq polymerase

Answer 32

used in PCR for DNA synthesis because it can withstand hot temperatures