DNA Replication

Question 1

Conservative model of replication

Answer 1

Parent molecules rejoin after replication or parent strands stay together during replication
Incorrect model of replication

Question 2

Semiconservative model of replication

Answer 2

Parent strand is used as template and joins with new strand

Correct model of replication

Question 3

Dispersive model of replication

Answer 3

Parent and new strands are cleaved: 1 strand could contain both new and old pieces
Incorrect model of replication

Question 4

Initiation of replication steps

Answer 4

1. Replicator sequence is denatured by initiator proteins to form a replication bubble
2. Helicase is loaded onto the DNA, breaking H-bonds between 2 strands
3. Helicase recruits primase
4. Primase synthesizes a short primer (made out of RNA and contains 5-10 nucleotides)

Question 5

Ori

Answer 5

Origin of replication in bacteria

Located at middle of replication bubble

Question 6

of replication forks in replication

Answer 6

2 replication forks (bidirectional)

Question 7

Replication steps

Answer 7

1. Single stranded binding proteins bind to the single stranded DNA in the fork, preventing strands from coming back together
2. DNA pol III adds nucleotides in 5’ to 3’ direction, synthesizing off of RNA primer
3. DNA gyrase relaxes the tension ahead of the replication fork

Question 8

Direction that DNA pol III reads template strand

Answer 8

3’ to 5’

Question 9

Joining of the Okazaki fragments/ end of replication

Answer 9

1. DNA pol I digests RNA primer ahead of it using its 5’ to 3’ exonuclease activity (cuts at end of DNA) and replaces primer with nucleotides in the 5’ to 3’ direction
2. DNA ligase seals the nick between adjacent Okazaki fragments

Question 10

dNTP

Answer 10

Deoxynucleoside triphosphate

Building blocks of DNA (nucleotides)

Question 11

“Primer” for DNA pol I

Answer 11

Okazaki fragments

Question 12

Fidelity

Answer 12

Accuracy of polymerase

Question 13

Processivity

Answer 13

How many dNTPs DNA pol can add before it falls off strand

Question 14

How many nucleotides are incorrect vs. how many are correct

Answer 14

About 1 in 1 million is incorrect

Question 15

Direction of exonuclease activity in DNA pols I and III

Answer 15

3’ to 5’ exonuclease activity

Removes incorrect 3’ dNTP, adds correct dNTP, and keeps going

Question 16

Replisome

Answer 16

Complex of proteins involved in replication

All enzymes act together in system simultaneously

Question 17

Differences between replication in prokaryotes and eukaryotes

Answer 17

1. Eukaryote chromosomes are longer and bigger (not circular)
2. Eukaryotes have multiple origins of replication per chromosome
3. Eukaryotes have 15 polymerases

Question 18

Replicon

Answer 18

DNA or RNA molecule that replicates from a single origin of replication
1 origin of replication to which 2 replication forks fuse

Question 19

Telomerase

Answer 19

Complex of protein (does synthesizing) and RNA (template) that helps maintain chromosome size (extends end of chromosome)
Adds telomeres
Reverse transcriptase: makes DNA from RNA template