Ch. 9 DNA Replication and Recombination

Question 1

semiconservative replication

Answer 1

only true process accepted. each of the original nucleotide strands remains intact conserved, despite no longer being combined in the same molecule; the original DNA molecule is half semi conserved during replication

Question 2

replicon

Answer 2

segment of DNA that undergoes replication

Question 3

theta replication

Answer 3

common type of replication that takes place in circular DNA such as found in E. coli and other bacteria.

Question 4

Replication bubble

Answer 4

unwinding of the double helix generates this loop

Question 5

replication fork

Answer 5

the point of unwinding where the two single strands separate from the double stranded dna helix.

Question 6

bidirectional replication

Answer 6

if there are two replication forks one at each end of the replication bubble, the forks proceed outward in both directions in this process

Question 7

DNA Polymerases

Answer 7

The enzymes that synthesize DNA, can add nucleotides only to the 3’ end of the growing strand. and so new dna strands always elongate in same 5’ to 3’ direction.

Question 8

leading strand

Answer 8

new strand which under goes continuous replication (w/o okazaki fragments because goes 5’ to 3’) Good boy strand

Question 9

Lagging strand

Answer 9

Bad boy strand. okazaki fragments. discontinuous replication.

Question 10

replication takes place in what 4 stages

Answer 10

• initiation
• unwinding
• elongation
• termination

Question 11

Initiator proteins

Answer 11

initiates unwinding to allow helicase and other single strand binding proteins to attach to polynucleotide strand

Question 12

DNA Helicase

Answer 12

breaks hydrogen bonds that exist between bases of two nucleotide strands of DNA molecule. Helicase can not initiate unwinding, thats why there are initiator proteins

Question 13

single strand binding proteins (SSBs)

Answer 13

After DNA has been unwound by helicase SSBs attach tightly to the exposed single stranded DNA.

Question 14

DNA gyrase

Answer 14

type of topoisomerase - another protein essential for the unwinding process. (topoisomerases control the supercoiling of DNA). reduces torsional strain (torque) that builds up ahead of the replication fork.

Question 15

Elongation

Answer 15

dna is synthesized with the use of Single stranded DNA as template. series of enzymes needed. this is where replication occurs.

Question 16

primase

Answer 16

type of rna polymerase. synthesizes short stretches of RNA nucleotides or “primers” which provide a 3’ OH group to which DNA polymerase can attach DNA nucleotides.

Question 17

DNA Polymerase 1

Answer 17

builder. removes and replaces primers. allows enzyme to synthesize dna and correct errors.

Question 18

DNA Polymerase 3

Answer 18

builder. elongates dna. adds new nucleotides to 3’ end of growing DNA strand.

Question 19

DNA ligase

Answer 19

Joins Okazaki fragments by sealing breaks in the sugar-phosphate backbone of newly synthesized DNA.

Question 20

Termination

Answer 20

some DNA molecules, replication is terminated when ever two replication forks meet. some have specific termination sites/sequences (Ter sites).

Question 21

proofreading

Answer 21

most of the errors that do arise in nucleotide selection are coorrected in this process.

Question 22

mismatch repair

Answer 22

corrects errors after replication is complete. “deformity” noticed from mismatch and then excised.

Question 23

replication licensing factor

Answer 23

factor that attaches to an origin of dna (origin of replication) allowing replication machinery to find it and begin. “permit to build”.

Question 24

ALPHA dna polymerase

Answer 24

NO 3’ to 5’ exonuclease activity. Initiation of nuclear DNA synthesis and DNA repair. has primase activity.

Question 25

DELTA dna polymerase

Answer 25

Lagging-strand synthesis of nuclear dna. dna repair, and translesion dna synthesis.

Question 26

EPSILON dna polymerase

Answer 26

Leading strand synthesis

Question 27

GAMMA dna polymerase

Answer 27

replication and repair of MITOCHONDRIAL dna.

Question 28

G overhang

Answer 28

The single stranded protruding end of the telomere. this can be extended by telomerase, an enzyme with both a protein and rna component.

Question 29

homologous recombination

Answer 29

exchange between homologous DNA moleecules.

Question 30

heteroduplex DNA

Answer 30

formed by single stranded dna molecule of one chromosome pairing with a single stranded dna molecule of another.

Question 31

Holliday junction

Answer 31

structure formed by single strand break in each of two dna molecules.