FOM 5.1.2

Question 1

Only 30% of conception events lead to live births, what is one of the main causes for this?

Answer 1

Chromosomal abnormalities leading to early spontaneous abortions

Question 2

What pattern does DNA replication follow?

Answer 2

semi-conservative

Question 3

DNA is always polmerized in what direction? What must be present?

Answer 3

5’ to 3’, template strand

Question 4

In what phase does DNA replication occur? How long does it take?

Answer 4

S phase, 6-12 hours

Question 5

What are the 5 main steps of DNA synthesis?

Answer 5

See image

Question 6

What is some important info about human origins of replication?

Answer 6

Some sequence bias: AT-rich CpG islands, variable depending on cell, transcriptionally active

Question 7

Describe the directionality of human DNA replication.

Answer 7

Bidirectional, leading strand and lagging strand

Question 8

An increased # of origins leads to what result?

Answer 8

Faster transcription

Question 9

What binds the ORI?

Answer 9

ORC (origin recognition complex)

Question 10

What couples w/ ORC to attract the helicase? What are the two components of the helicase?

Answer 10

cdc6; MCM helicase w/ cdt1 After MCM is bound w/ ORC, cdt1 and cdc6 dissociate

Question 11

What is the name of the inhibitor of Cdt1?

Answer 11

Geminin

Question 12

What are the three machinery involved in the replicative complex?

Answer 12

1)Primase enzyme (RNA->DNA) 2)DNA Polymerase deta/epsilon 3) Topoisomerase I

Question 13

What binds to ssDNA to protect it after DNA is unwound by MCM?

Answer 13

RPA (replication protein A)

Question 14

What are the two steps in the synthesis of the primer for replication?

Answer 14

1) Primase: 10-15 nt RNA 2) DNA pol alpha ~30 nt DNA onto RNA

Question 15

What interacts w/ DNA pol d/e to help it stay bound to ssDNA?

Answer 15

PCNA

Question 16

The leading strand creates a continuous strand whereas the lagging strand is discontinuous and makes ____.

Answer 16

Okazaki fragments

Question 17

What does topoisomerase I do?

Answer 17

It creates a single stranded nick that allows for unwinding, which prevents “overwinding”

Question 18

What links together the okazaki fragments?

Answer 18

DNA ligase by creating a phosphodiester bond

Question 19

What removes and moves histones during DNA replication?

Answer 19

Chaperones

Question 20

What problem is solved by telomerase?

Answer 20

It’s a reverse transcriptase that can preserve telomere length on the lagging strand.

Question 21

Describe the telomere length over time in the three cell types (germ, stem, normal somatic)

Answer 21

See image

Question 22

What is true about telomere length in persons with an increased mortality risk?

Answer 22

Shorter

Question 23

As perceived affluence increases, what happens to the telomeres?

Answer 23

Longer

Question 24

What is the mechanism of action of Acyclovir in the treatment of herpes? Foscarnet?

Answer 24

Chain terminator; DNA polymerase inhibitor (noncomp - blocks pyrophosphate binding site)