FINAL - Lecture 12

Question 1

The central enzyme involved in DNA replication is:

Answer 1

DNA polymerase III (pol III)

Question 2

DNA synthesis begins from:

Answer 2

the end of a preexisting DNA or RNA primer

Question 3

DNA synthesis begins from the end of a preexisting DNA or RNA primer, it transcribes :

Answer 3

the complimentary strand called the DNA TEMPLATE

Question 4

The elongating new strand is ALWAYS extended from:

Answer 4

The 5’ end toward the 3’ end

Question 5

which enzyme unwinds (relaxes the supercoiling) the double strands

Answer 5

topoisomerase

Question 6

which enzyme breaks the hydrogen bonds of the two strands

Answer 6

helicase

Question 7

__ temporarily stabilize the single strands

Answer 7

single stranded binding proteins

Question 8

DNA synthesis is primed by:

Answer 8

RNA primers

Question 9

Because DNA is synthesized
in a 5’ to 3’ direction,
one strand is synthesized
____,
the other ____.

Answer 9

Because DNA is synthesized in a 5’ to 3’ direction, one strand is synthesized continuously and the other in short discontinuous steps

Question 10

Okazaki fragments are:

Answer 10

The newly synthesized DNA strands on the lagging strand that have not been ligated to the the long continuous newly synthesized strand

Question 11

The leading strand has:

Answer 11

continuous replication

Question 12

the lagging strand has:

Answer 12

discontinuous steps at replication

Question 13

on the lagging strand, when each new stretch reaches the previously replicated section ___

Answer 13

the RNA primers are removed

Question 14

The discontinuous pieces of new DNA on the lagging strand are connected by;

Answer 14

Covalent bonds by DNA ligase

Question 15

Pol I, pol II and pol III have two activities:

Answer 15

(1) 5’ to 3’ DNA synthesis
(2)exonuclease activity: they can run in reverse in the 3’ to 5’ direction and remove incorrect bases that have been added

Question 16

There is a __ origin of replication on an E. coli chromosome

Answer 16

single

Question 17

After initiation in E.coli, replication proceeds:

Answer 17

in both directions with two replication forks

Question 18

E. coli have:

Answer 18

bidirectional replication

Question 19

Due to bidirectional replication of an E.coli chromosome, there is a need for:

Answer 19

Unwinding of the DNA (the need for helicases: breaking hydrogen bonds)

Question 20

Eukaryotic chromosomes have __ origins of replication

Answer 20

multiple

Question 21

Do eukaryotic chromosomes have bidirectional replication?

Answer 21

yes

Question 22

telomerase:

Answer 22

replicates repeated DNA sequences at the ends of eukaryotic cchromosomes. It carries its own RNA template

Question 23

Telomerase is a : specialized reverse transcriptase

Answer 23

specialized reverse transcriptase

Question 24

HIV is a :

Answer 24

retrovirus (it uses reverse transcriptase to synthesize DNA from an RNA template)

Question 25

How can we replicate DNA in a test tube?

Answer 25

1. Melt the DNA to single stranded molecules with high temperature (95C)
2. Add primer
3. Add DNA polymerase and nucleotides (dNTPS)

Question 26

Why do we say that DNA polymerase III is a DNA dependant polymerase?

Answer 26

because it always uses a preexisitng DNA molecule as a template for replication

Question 27

DNA synthesis uses __ as substrates to add ___ to the growing DNA chain

Answer 27

DNA synthesis uses nucleotide triphosphates as substrates to add nucleotide monophosphates to the growing DNA chain

Question 28

For each nucleotide added, a __ is released

Answer 28

pyrophosphate

Question 29

The elongating new strand is always extended from:

Answer 29

the 5’ end toward the 3’ end

Question 30

The replication enzymes
move down the template
strand in the

Answer 30

3’ to 5’
direction.

Question 31

enzymes have:

Answer 31

specific substrate binding domains

Question 32

Proof reading removes:

Answer 32

mis-paired bases