KA2: replication of dna

Question 1

why does dna polymerase replicate the dna before division?

Answer 1

ensures every cell contains ALL genetic information

Question 2

what is cell division important for in multicellular and unicellular organisms?

Answer 2

M: growth and repair
U: reproduction

Question 3

what does semi conservative replication mean?

Answer 3

when the two strands nucleotides separate, and they act as a template for free nucleotides to bind to

Question 4

dna polymerase can only join __________ onto the _______ of the template strands.

Answer 4

nucleotides
3’ end

Question 5

what does dna polymerase need to start replication?

Answer 5

primers

Question 6

what is the role of a primer during replication?

Answer 6

it binds to the 3’ end of the TEMPLATE STRAND allowing dna polymerase to add dna nucleotides to the new strand being formed

Question 7

what does dna polymerase do once attached to the primer?

Answer 7

it is an enzyme which adds dna nucleotides using complementary base pairing to the 3 (deoxyribose)end of the new dna strand being made.

Question 8

what happens once the dna is unwound?

Answer 8

the hydrogen bonds between the bases break forming two template strands.

Question 9

which end does the dna primer bind to & what does this enable/why is a primer required?

Answer 9

3 end of template strand
dna polymerase can only extend existing strands hence why primer needed.

Question 10

DNA polymerase can
only add DNA nucleotides in one _________
resulting in the _______ strand being
replicated continuously and the lagging
strand replicated in __________.

Answer 10

direction
leading
fragments

Question 11

why can’t nucleotides be added to the 5 end of the template strand?

Answer 11

dna polymerase can only add nucleotides in a 5 to 3 direction.
(primers bind to the 3 end primer: 5–3 +++ nucleotides

Question 12

____ primers attach along the lagging strand then are extended by dna ________ then the fragments are joined by the enzyme _______.

Answer 12

many/multiple
polymerase
ligase

Question 13

what is the role of ligase during replication?

Answer 13

joining the fragments of dna together

Question 14

in pcr, primers are short strands of __________ which are ____________ to specific target sequences at the two ends of the region of DNA to be ________

Answer 14

nucleotides
complementary
amplified

Question 15

what does PCR allow for?

Answer 15

specific sections of dna to be amplified in vitro using complementary primers for specific target sequences.

Question 16

repeated cycles of ……… amplify the _____ region of dna.

Answer 16

heating and cooling
target

Question 17

what happens during stage 1 of pcr: dna denaturation?

Answer 17

the dna is heated to between 92-98 degrees - the hydrogen bonds break and strands separate

Question 18

what happens during stage 2 of pcr: primer annealing?

Answer 18

it is then cooled to between 50 - 65 degrees allowing primers to bind to the target sequences.

Question 19

what happens during the final stage of pcr: primer extension?

Answer 19

heated again to between 70 - 80 degrees which allows a heat tolerant DNA polymerase to replicate the region of
DNA (taq-polymerase)

Question 20

what are primers and their role during pcr?

Answer 20

primers are short strands of
nucleotides which are complementary to
specific target sequences at the two ends of the regions of dna to be amplified
they give the dna polymerase a starting point/ allows dna nucleotides to be added

Question 21

what are some practical applications of pcr ?

Answer 21

help solve
crimes, settle paternity suits, and diagnose
genetic disorders.