Replication initiation & termination, Polymerization errors

Question 1

True or False: DNA replication is bidirectional, meaning that 2 replication forks emerge from each origin.

Answer 1

True

Question 2

In prokaryotes, such as the circular E. coli chromosome, replication is initiated at a _____ location. This DNA sequence is known as ____.

Answer 2

single

oriC

Question 3

OriC is rich in ______ and ______, because these nucleotides have a lower melting temperature and allow for faster separation.

Answer 3

adenine

thymine

Question 4

True or False: Although bacteria has one origin of replication, it can initiate replication more than once in a cell cycle.

Answer 4

True

Question 5

In bacteria, ____ is replicated so there is a new origin and they start doing replication on there as well.

Answer 5

oriC

Question 6

When are catenated chromosomes formed?

Answer 6

After DNA replication and before Topo 4 splits the strands apart

Question 7

In contrast to prokaryotes, eukaryotes have ____ origins of ________.

Answer 7

many

replication

Question 8

True or False: Since eukaryotes have many origins of replication, there needs to be _____ _______.

Answer 8

tight regulation

Question 9

What is the mechanism behind tight regulation of the origins of replication?

Answer 9

At each origin of replication, there’s licensing machinery

Question 10

When beginning DNA synthesis, ________ proteolysis is used to get rid of licensing machinery at only __ origin of replication.

Answer 10

ubiquitin

one

Question 11

To resolve the issue of the “end problem” with linear chromosomes, ________ extend the overhanging ___ end with short ____ repeat sequences.

Answer 11

Telomerases
3’
Telomere

Question 12

Telomerase is a ___________, meaning that it is a protein that contains RNA.

Answer 12

ribonucleoprotein

Question 13

True or False: Normally, somatic cells do not express telomerase. However, _____ ____ do express telomerase to ensure that offspring are born w/ long telomeres.

Answer 13

germ cells

Question 14

Cells spend ____ and ____ in exchange for accuracy.

Answer 14

energy, time

Question 15

Name different kinds of mutations

Answer 15

1. Base substitutions (2 types)
2. Insertions and deletions (indels)
3. Breaks in the backbone

Question 16

What are two types of base substitutions?

Answer 16

1. Transitions

2. Transversions

Question 17

What is a transition?

Answer 17

When a purine is switched to another purine, or when a pyrimidine is switched to another pyrimidine (A–>G) or (T–>C)

Question 18

What is a transversion?

Answer 18

When a purine is switched to a pyrimidine (A–>C) or when a pyrimidine is switched to a purine (T–>A)

Question 19

True or False: The hemagglutinin (HA) protein of influenza is what is used to enter host cells. Thus, it is constantly undergoing rapid evolution to evade the immune system.

Answer 19

True

Question 20

True or False: Mutations MUST arise during DNA (or RNA) replication.

Answer 20

True

Question 21

Name 3 of Darwin’s different ideas used to explain biological diversity

Answer 21

1. Variation
2. Heritability
3. Differential survival

Question 22

As genomes get larger, there is a _______ in mutation rate in contrast to smaller genomes.

Answer 22

Decrease

Question 23

Name 3 mechanisms of reducing mutations

Answer 23

1. Inherent accuracy
2. Proofreading
3. DNA repair & surveillance

Question 24

The imino tautomer of adenine base pairs to ______ instead of _______.

Answer 24

cytosine

thymine

Question 25

____ ________ proofreads the nascent strand. The _____ and _____ close over the nucleotide when the correct nucleotide is added, thus making it more likely to be added to the growing chain.

Answer 25

DNA polymerase

finger, thumb

Question 26

in DNA polymerase, the ______ domain is the proofreading site

Answer 26

palm

Question 27

True or False: DNA poly 3’-5’ exonuclease has no idea what it is chewing off.

Answer 27

True

Question 28

How does DNA poly 3’-5’ exonuclease know that the incorrect nucleotide was put on?

Answer 28

The wrong nucleotide does not base pair well and the mismatch makes the duplex unstable, leading to DNA melting and forming a single strand. The single strand flops down to the proof reading site where it’s chewed off.

Question 29

What are the 2 exonuclease activities of DNA Pol I?

Answer 29

5’ to 3’ exonuclease chews off RNA primers

3’ to 5’ exonuclease proofreads for accuracy

Question 30

DNA _______ _ also has proofreading activity, but it is unable to chew off primers

Answer 30

DNA pol 3

Question 31

Name 3 DNA intercalating agents that are able to cause indels

Answer 31

1. Proflavin
2. Acridine orange
3. Ethidium