Lecture 9: DNA Replication

Question 1

Requirements for synthesis of DNA

Answer 1

1) ALL four dNTP
2) Fragment of DNA to act as template
3) DNA polymerase
4) Mg2+ (Co-enzyme for DNA polymerase)
5) Primerase (3’ -OH group)

Question 2

Function DNA Ligase

Answer 2

-Forms phosphodiester bonds

(Between phosphate and OH) -Taking out water

Question 3

Structure of DNA and RNA

Answer 3

1) Peptide bond (linear)
2) Hydrogen bonds
3) Disulfide bonds
4) polypeptide bonds (multiple)

Question 4

ribosomal rna

Answer 4

RNA that gets translated

Question 5

MiRNA

Answer 5

1) Translation of target DNA repressed

2) or degraded

Question 6

ATP

GTP

UTP

CTP

Answer 6

Provide energy

ATP- Universal energy

GTP-protein synthesis

UTP-Glycogen

CTP-Activation of reactants in phospholipids biosynthesis

Question 7

snRNA

Answer 7

Involved in splicing and gene regulation

Question 8

DNA replication:

Eukaryotes

Answer 8

-Many replications of origin Initiation proteins= begin unwinding DNA strands)

1) Helicase unwinds DSDNa into single strands
2) Dna primase: Primes area for replication
3) DNA polymerase- alpha: Removes primase (No exonucelus acitvity)
4) DNA polymerase-gamma: Synthesizes DNA (3’–>5’)

• Topoisomerase I and II: Relieves supercoilings
• Telomerase= noncoding region, susceptible to mutation (tolermerase helps combat this)

Question 9

DNA replication:

Prokaryotes

Answer 9

• One replication site (Initiation proteins= begin unwinding DNA strands)
  1) Helicase completely unwinds DNA
  2) DNA Primer

3) DNA polymerase I: Removes primer, (5’–>3’)
replacing w DNA,
-but (3’–>5’ when proofreading)

4) DNA Polymerase III: Elongates DNA (5’–>3’) exonucelus activity (synthesizes leading, lagging strand, okazaki fragments in leading strands)
5) DNA Polymerase II: Repairs damaged DNA (3’–>5’) exonucelus activity, before RNA can be synthesized
- Single Stranded binding proteins (ssb): Binds to replication fork, Prevents strands from reannealing
- Clamp proteins: Hold DNA polymerase onto template for synthesize of long templates (Okazaki fragments)
- DNA gyrase (topoisomerase II): Relieves positive superocoils by incorporating negative supercoils

Question 10

Major differences between Pro and Euk replication

Answer 10

1) # replication sites
2) RNA primer
3) Different DNA polymerase