DNA Synthesis

Question 1

what is the template involved in semiconservative replication

Answer 1

One strand of the DNA molecule

Question 2

What is the first step of DNA synthesis

What’s the difference between eukaryotes and prokaryotes

Answer 2

Their is an origin of replication that opening so that DNA starts synthesizing

• many replication forks =e
• one replication fork: p

Question 3

Explain using a diagram the first step of DNA synthesis

Answer 3

Answer includes

• replication fork both sides
• explains leading and lagging strands
• explains okazaki fragments

Question 4

Difference between leading and lagging strands?

Answer 4

leading is towards replication fork

lagging away from the replication fork

Question 5

Helicase

Answer 5

Breaks h bonds and unwinds the double helix

Question 6

Topoisomerase

Answer 6

Relaxes supercoiled DNA

Question 7

DNA Polymerase

Answer 7

Replace RNA primers with DNA nucleotides

- II synthesizes DNA in the 5’ to 3’ direction on leading and lagging strands

Question 8

Single stranded binding protein

Answer 8

Coats single stranded DNA

Question 9

Primase

Answer 9

synthesizes RNA primers on leading and lagging strands

- RNA primers are used for DNA poly. to bind onto DNA

Question 10

DNA ligase

Answer 10

catalyzes phosphodiester bond formation and joins DNA fragments

Question 11

Synthesis of leading strand steps

Answer 11

• A replication fork opens and replication begins with synthesis of RNA primase
• The topoisomerase relaxes the DNA strands
• Helicase opens up the DNA\
• single strand binding protein keeps strands apart
• The DNA polymerase starts synthesis in he 5-3 direction
• Initial primase is removed by DNA polymerase and fills space with DNA
• DNA ligase seals the gap

Question 12

Chargaff Rules

Answer 12

• different species have different ratios of AT and CG
• in each species amount of adenine - #thymine
  and the amount of thymine = guanine

Question 13

Summary of lagging strand

Answer 13

• DNA opens, SSBP bind, primase synthesizes RNA primer
• DNA polymerase synthesizes DNA 5-3 direction using okazaki fragments
• DNA pol. removes primer and DNA ligases seals the gap

Question 14

Difference between DNA Replication and PCR

Answer 14

DNA Rep

• uses helicase to separate 2 strands, PCR uses heat
• Primers are made out of RNA, PCR primers are made out of DNA
• contains leading and lagging strands, PCR has no leading and lagging strand because only short fragments are used

Question 15

Explain Telomerase

Answer 15

• on the lagging strand their is a part of DNA that does not get synthesized which means that as time progresses DNA gets shorter, telomerase can fix this but its too dangerous because because it causes cells to multiply forever causing cancer.

Question 16

Is an error in replication the same as a mutation?

Answer 16

NO, an error happens when the wrong base is placed during DNA replication

Question 17

Is DNA damage the same as a mutation?

Answer 17

No

Question 18

How and when do mutations happen?

Answer 18

a mutation happens when the error is not fixed and the change is not part of the genome
an error only becomes a mutation if it survives the second round of replication

Question 19

What triggers the proofreading response of the DNA polymerase?

Answer 19

• the addition of a wrong nucleotide altering the geometry of the DNA

Question 20

Types of mutations

Answer 20

Frameshift: insertion of deletion
Nonsense: mutations that produce stop codons
missense: change the amino acid that’s coded
Silent: mutation does not change the amino acid being coded