replication of DNA

Question 1

what is a primer

Answer 1

a short strand of nucleotides which binds to the 3’ end of the template DNA stand

Question 2

what is cell division

Answer 2

when the nucleus divides itself forming 2 new daughter cells which have the same genetic material

Question 3

leading strand

Answer 3

1. DNA unwinds and weak hydrogen bonds break (Y shaped fork, 2 template strands)
2. DNA polymerase can add on complementary nucleotides to the exposed bases only at 3’ end
3. continuous replication of leading strand as nucleotides can only add in 5’ to 3’ direction
4. at replication fork nucleotides align w complementary bases
5. DNA polymerase forms covenant bond. strand extends from primer in one direction. primer replaced by DNA nucleotides
6. new strand is leading strand because its replicated continuously as original DNA double helix unwinds

Question 4

lagging strand

Answer 4

• new DNA strand replicated in fragments
  1. DNA polymerase adds new nucleotides to 3’ ends for primers
  2. after DNA fragment is replicated its primer is replaced by DNA nucleotides
  3. ligase joins fragments of DNA by forming covenant bonds
  4. complementary DNA form hydrogen bonds - now 2 DNA molc
• original DNA replicated and each double helix has original and new strand

Question 5

how is genetic info stored and passed on

Answer 5

stored as a base sequence of DNA and passed from cell to cell in growth and one gen to another in reproduction

Question 6

PCR

Answer 6

process which amplifies sections of DNA in a lab
- reaction mixture contains DNA polymerase, DNA sample, DNA nucleotides, primers and ATP

Question 7

stages of PCR

Answer 7

1. DNA heated between 92 and 82 to break weak bonds and separate stands denaturing DNA
2. cooled between 50 and 65 to allow primers to bind to target sequences of DNA - bases are complementary to specific target sequences at 2 end frangments of DNA to be amplified
3. heated between 70 and 80 to enable heat tolerant DNA polymerase to replicate region of DNA

Question 8

what is PCR used for

Answer 8

to solve crimes, settle paternity suits and diagnose genetic disorders

Question 9

why are 2 different primers needed

Answer 9

they each bind to a different strand, stands are complementary

Question 10

stages of PCR in temps

Answer 10

DENATURATION: 92 - 98
ANNEALING: 50 - 65
EXTENTION: 70 - 80

Question 11

what is amplification

Answer 11

when process is repeated and region of interest is amplified exponentially

Question 12

which molecules are required in the replication of the lagging strand of a DNA molecule?

Answer 12

DNA polymerase, ligase and primers

Question 13

explain why only the leading strand can be replicated continuously

Answer 13

DNA polymerase adds nucleotides to 3’ end of primer

Question 14

name the enzyme that joins fragments together in the lagging
strand

Answer 14

ligase

Question 15

state why the antiparallel nature of the DNA molecule results in
one of the strands being synthesised in short fragments

Answer 15

nucleotides added to 3́́′ end

Question 16

which molecules are required in the replication of the lagging strand of a DNA molecule?

Answer 16

DNA polymerase, ligase, primer