lecture 20

Question 1

where does theta replication occur the most

Answer 1

-replication that occurs in most circular
DNA

Question 2

what is the direction of the theta DNA replication

Answer 2

DNA replication is bidirectional

Question 3

explain the process of theta DNA replication

Answer 3

double strand DNA start to unwind at the origin of replication. By producing single strand DNA as a template then the new DNA would synthesis. A replication bubble would form with two replication fork at each side. At the end of the process two circular DNA rings will produce

Question 4

where does the rolling circle replication occur the most

Answer 4

specialized form of replication that
occurs in the F factor and some viruses

Question 5

explain the process of rolling circle replication

Answer 5

replication is initiated at the break in one of the nucleotide strands. DNA synthesis start at the 3’ and the inner circle serve as a template and then 5’ start to displace. by the end of the process we will have one single-strand DNA and a double strand CIRCULAR DNA. the linear DNA can be circulated and serve as a template for a new DNA .

Question 6

what is the final product of the rolling circle replication

Answer 6

the production of rolling circle replication is multiple circular DNA molecules and

Question 7

how is the direction of the rolling circle replication

Answer 7

unidirectional

Question 8

where does the linear chromosomes replication occurs

Answer 8

occurs in the linear chromosomes of eukaryotic cells.

Question 9

explain the process of linear chromosomes replication?

Answer 9

linear chromosomes have multiple origin of replication and at each origin DNA start to unwind and replication bubble. DNA synthesis take place on both strands at each end of the bubble as the replication wind proceed outward. the bubbles run into each others and producing two identical linear DNA strands

Question 10

what is the final production of the linear chromosome replication

Answer 10

two identical linear DNA strands

Question 11

what is the direction of the linear chromosome replication

Answer 11

it is bidirectional

Question 12

what does DNA replication requires

Answer 12

• Magnesium (Mg2+)
• DNA dependent DNApolymerase
• Four deoxyribonucleoside triphosphates (dNTPs)
• A template DNA to becopied
• An RNA primer (provides the 3’-OH end to initiateDNA synthesis by DNApolymerase)

Question 13

what is the synthesis direction of the DNA

Answer 13

• DNA is always synthesized in the 5’ to 3’direction

Question 14

Is the newly synthesis DNA strand parallel to the parental strand

Answer 14

• Newly-synthesized DNA strand is complementary and anti-parallel to
  the parent strand

Question 15

how do the complementary strands held together

Answer 15

• DNA strands are held together by hydrogen bonds between complementary bases

Question 16

in the replication how do the nucleotides connect to each others

Answer 16

in the replication the 3’-OH group of the last nucleotide connects to the strand attached to the 5’-phosphate group of the incoming dNTP

Question 17

what is the type of bond between the two nucleotides

Answer 17

phosphodiester bond

Question 18

alpha phosphate is attached to which part

Answer 18

alpha (α) phosphate group attached to the 5’ carbon or the 3’carbon of the deoxyribose sugar.

Question 19

DNA synthesis is …………..on the leading strand and …………on the lagging strand

Answer 19

DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand

Question 20

what is Okazaki

Answer 20

short DNA fragments produced by discontinues synthesis

Question 21

how is the direction of lagging strand

Answer 21

lagging strand produce discontinues fragments in the opposite direction of the unwinding

Question 22

how is the direction of the leading strand

Answer 22

direction of the leading fragment is in the direction of the unwinding DNA

Question 23

What is the replication origin call in the e coli

Answer 23

oriC

Question 24

in DNA replication which site would be the origin of replication

Answer 24

AT rich site

Question 25

what is the DNA helicase

Answer 25

DNA helicase unwinds the DNA in the 5’ to 3’ direction: it travels on the lagging strand ahead of the replication machinery
-unwound single-stranded DNA is coated with single-strand binding protein to keep DNA single-stranded.

Question 26

what is DNA gyrase

Answer 26

it relieve DNA strands ahead of replication fork

Question 27

why we need gyrase

Answer 27

Helicase-induced unwinding of the double helical DNA causes the DNA ahead of the helicase to be overwound producing positive supercoils that would stop replication. In bacteria, a specialized DNA topoisomerase II (DNA gyrase) nicks the DNA and releases the positive supercoils.

Question 28

what does DNA primase do

Answer 28

-DNA primase synthesizes a short RNA primer that provides the 3’ OH end for DNA polymerase to begin DNA synthesis leading strands start first followed by lagging strands

Question 29

on which strand we can find the primase

Answer 29

at the leading strand the primer is required at the 5- end of the newly synthesized strand

Question 30

where does the primer generate at the lagging strand

Answer 30

on the lagging strand where replication is discontinuous, a new primer must be generated at the beginning of each Okazaki fragment

Question 31

what does Replication mechanism requires:

Answer 31

Replication mechanism requires:
- topoisomerase
- helicase
- Single-strand DNA binding protein (SSB)
- DNA primase
- DNA polymerase III (plus β clamp)
- DNA polymerase I
- DNA ligase