Molecular biochemistry W2

Question 1

What happens in C1 of cell cycle

Answer 1

Cell growth

Question 2

What happens in S phase of cell cycle

Answer 2

• DNA synthesis

Question 3

Why is DNA replication semiconservative

Answer 3

As each DNA molecule contains one old and one new strand

Question 4

What happens in G2 phase of cell cycle

Answer 4

• Preperation for mitosis

Question 5

Explain how DNA is prepared for Replication

Answer 5

• Chromatin remodelling factors modify or replace proteins in chromatin to allow acces to DNA
• Nuclear DNA is replicated in the S phase of the crll

Question 6

Where does DNA replication start

Answer 6

Starts at ORIs( origins of replications)

Question 7

Where do replication forks form

Answer 7

Form at ORIs

Question 8

Name the 3 enzymes involved in DNA replication

Answer 8

-DNA polymerase a
-DNA polymerase delta
-DNA ligase

Question 9

What is the function of DNA polymerase a - alpha

Answer 9

• Initiates replication but lack proofreading ability

Question 10

What is the function of DNA polymerase delta

Answer 10

• Performs most DNA synthesisand hass proofreading function

Question 11

What is the function of DNA ligase

Answer 11

• Joins Okazaki fragments by sealing gaps between them

Question 12

What is the function of DnaA

Answer 12

• Binds ori and starts strand seperation

Question 13

What is the function of DNA helicase

Answer 13

• Unwinds DNA using ATP

Question 14

What is the function of SSB proteins

Answer 14

• Bind and stabilize single stranded DNA

Question 15

What is the main function of Topoisomerases

Answer 15

• Stop supercoiling

Question 16

What is the function of Topisomerases Type 1

Answer 16

• It Cuts 1 strand + require no ATP

Question 17

What is the function of Topoisomerases Type 2

Answer 17

Cuts both strands + uses ATP

Question 18

What is the function of the leading strand in DNA synthesis

Answer 18

• Continues synthesis

Question 19

What is the function of thr lagging strand in DNA synthesis

Answer 19

• Disconitnues synthesis in OKazaki fragments

Question 20

What does DNA polymerase require to start synthesis

Answer 20

• RNA primer

Question 21

What is the function of the enzymes in Prokaryotc replication:
- Primase
-DNA Pol III
-DNA Pol I
-DNA ligase

Answer 21

-Primase: Synthesizes RNA primers
-DNA POL 111- Enzyme for elongation
DNA Pol 1- Removes RNA primers
DNA ligase: Joins fragments with phosphodiester bonds

Question 22

What are Telomeres

Answer 22

• They are repetitive noncoding DNA and proteins at chromosome ends

Question 23

What is Telomerases

Answer 23

• They are a reverse transcriptase

Question 24

Where are Telomerases active

Answer 24

• Active in germ cells,stem cells and cancer cells

Question 25

Where are Telomerases inactive

Answer 25

Somatic cells

Question 26

What is the function of polymerase a

Answer 26

- Starts synthesis

Question 27

What is the function of polymerase delta δ

Answer 27

Extends the lagging strand , Hass proofreadingW

Question 28

What is the function of polymerase ε

Answer 28

Extend the leading strand + has proof reading

Question 29

What is the function of polymerase beta

Answer 29

- Used in DNA repair

Question 30

What is the function of polymerase γ

Answer 30

- Replicates mitochondrial DNA