Molecular biochemistry W2 redo

Question 1

What does semiconservative mean in DNA

Answer 1

Each new DNA molecular has 1 parental strand and one newly synthesized strand

Question 2

What do the template-directed DNA polymerase in porkaryotic replication require

Answer 2

• Mg 2+, and high fidelity

Question 3

In prokaryotic replication what does DNA polymerase use as a template

Answer 3

• Uses single stranded DNA (ssDNA)

Question 4

Explain how replication forks form + replication bubbles

Answer 4

• As the DNA rewinds , two replication forks form and move bidirectionally, forming a replication bubble

Question 5

Name the 3 key proteins involved in initiation and fork progression in prokaryotic replication

Answer 5

• DnaA protein
  -DNA helicase( DnaB)
  -SSBs( single stranded DNA binding proteins)
  -

Question 6

What is the function of DnaA
-What it binds to + what it causes

Answer 6

• Binds to DnaA boxes in oriC
• Causes local melting of AT-rich regions

Question 7

What is the function of DNA helicases+ what does DNA helicase activity cause

Answer 7

• Bind to ssDNA and unwind the double helix, using energ7 from ATP hydrolysis
  -Dna helicase activity causes supercoiling ahead of the replication

Question 8

What is the other name for DNA helicases

Answer 8

• DnaB

Question 9

What does DNA helicase loading require

Answer 9

• DnaC

Question 10

What is the function of single stranded DNA binding proteins(SSBs)
-How does it bind
-And why does it bind

Answer 10

-Binds cooperatively to ssDNA to:
-Prevent strands from reannealing
-Stabilize ssDNA for rep;ication
-Protect ssDNA from degradation by nucleases

Question 11

What does supercoiling result from

Answer 11

• Twisting DNA

Question 12

What is postive supercoils and location

Answer 12

overwinding ahead of the replication fork

Question 13

What is negative supercoils and location

Answer 13

underwinding and it is behind the fork

Question 14

What do supercoils interfere with

Answer 14

• DNA strand seperation

Question 15

How is supercoiling stopped

Answer 15

By DNA topoisomerases, which relieve supercoils by cutting and resealing DNA strands

Question 16

Name the 2 types od DNA topoisomerases

Answer 16

• Type 1 and type 2 DNA topoisomerases

Question 17

What is the 3 functions of type 1 DNA topisomeraases

Answer 17

• It Cuts one strand of DNA
  -Stores and reuses the energy from the broken phospjodiester bond
  -Relaxes supercoils

Question 18

What does type 1 DNA topisomerase not require

Answer 18

• Doesnt reuire ATP

Question 19

wHAT Is the 2 function of type 2 topisomerases + what does it require

Answer 19

• Cut both strands of DNA
• Relieves both postive and negative supercoils
  -requires ATP

Question 20

What is the function of DNA gyrase in type 2 dna topoisomerase

Answer 20

• introduces negative supercoils
  -Helps during replication and transcription by easing DNA unwinding

Question 21

Explaimn how DNA polymerase works

Answer 21

• reads the template strand in 3-5 direction
  -Synthesizes the new strand in the 5 - 3 direction

Question 22

How is the leading strand synthesized

Answer 22

• synthesized continuously in the sam direction as the replication fork movement

Question 23

How is the lagging strand synthesized

Answer 23

It is synthesized discontinuosly in the opposite direction of the replication fork

Question 24

How is the lagging strand made

Answer 24

• iMade in short segments called okazaki fragments joined together by DNA ligase

Question 25

Why cant DNA polymerase start synthesis

Answer 25

it needs a primer

Question 26

What is the RNA primer

Answer 26

Short RNA strand base paied to the DNA template

Question 27

What is primase+ function + what does it use as substrates + what does it release

Answer 27

Specialsied RNA polmerase that synthesizes the short RNA primer - uses ribonucleoside triphosphates as substrates and release pyrophosphate

Question 28

What is a primosome- what does it include

Answer 28

A complex including primase and prepriming proteins

Question 29

What does primosome make and initiate

Answer 29

It makes RNA primers on both strands and initiates okazaki fragment synthesis

Question 30

How does DNA polymerase extend the chain in + what is the substrate + what does it release

Answer 30

Extends the chain by adding deoxyribonuclotides to the 3 end of the primer - 5-DNTPS is substrate and releases PPi

Question 31

Which DNA polymerase carrys out proofreaing and why

Answer 31

DNA pol 3 + To make sure the bases added are complelemntary, if not hey are removed and replaced with the right one

Question 32

What does DNA polymerase 1 do

Answer 32

Removes RNA primer nucleotides

Question 33

What is the function fo DNA polymerase 2 and 3

Answer 33

It removes mismatched DNA

Question 34

Which DNA pol synthesixes the new strand

Answer 34

DNA POlymerase 3

Question 35

When does termination occur

Answer 35

It ocurs when the Tus protein binds to Ter sites on the DNA

Question 36

what happens in G1 phase: s phase G2 phase Mitosis

Answer 36

G1 (Gap 1): Prepares for DNA synthesis. S (Synthesis): DNA is replicated. G2 (Gap 2): Prepares for mitosis. M (Mitosis): Cell division occurs.

Question 37

Which eukaryotic DNA polymerase initates synthesis

Answer 37

- Pol a

Question 38

What is the function of Pol ε:

Answer 38

Synthesizes leading strand.

Question 39

What is the function of Pol δ:

Answer 39

Elongates Okazaki fragments on lagging strand.

Question 40

What is the function of Pol β and Pol γ

Answer 40

Pol β: Functions in DNA repair. Pol γ: Replicates mitochondrial DNA.

Question 41

What are telomeres

Answer 41

DNA protein complexes at chromosome ends

Question 42

Where do telomeres shorten

Answer 42

- Somatic cells

Question 43

WHat 3 cells maintain the length of telomeres and what do they use

Answer 43

stem, germ and cancer cells They ise telomerase

Question 44

What is the structure of telomerase

Answer 44

- A ribonucleoprotein with: -TERT(reverse transcriptase) -TERC( RNA template)

Question 45

What does telomerase allow DNA pol a to do

Answer 45

synthesize the complemetary strand

Question 46

What do reverse transcriptases convert

Answer 46

ssRNA to dsDNA

Question 47

What are histones

Answer 47

postively charged proteins

Question 48

Name examples of histones

Answer 48

- H1, H2A, H2B, H3 and H4

Question 49

Name which histones DNA wraps around

Answer 49

- H2A, H2B, H3 ,H4