DNA Repliction

Question 1

Name the model for DNA Replication

Answer 1

Semi-conservative replication

Question 2

Name the four requirements for DNA replication

Answer 2

four types of nucleotides
both strands of DNA
Enzyme = DNA polymerase
source of chemical energy to drive the process

Question 3

Explain the steps in DNA replication

Answer 3

DNA Helicase ( enzyme ) breaks the Hydrogen bonds linking the base pairs
Double helix unwinds into 2 strands
Each exposed polynucleotide strand acts as a template which complementary free nucleotides bind by a specific bae paring
Nucleotides join via condensation reaction by DNA Polymerase ( enzyme ) to form the missing strand
Each DNA molecule contains one of the og strands

Question 4

Name of the broken fragments on the antiparallel strand

Answer 4

okazaki fragments ( DNA Ligase joins this together

Question 5

Name the 2 incorrect models of DNA replication

Answer 5

Conservative model = og DNA molecule remains intact,
the daughter DNA is made out of entirely new molecules

Dispersive model = new and old DNA is dispersed in the newly synthesised DNA

Question 6

Name the nitrogen experiment

Answer 6

Meselson and Stahl Experiment

Question 7

Explain the Meselson and Stahl Experiment

Answer 7

ALL BASES IN DNA CONATIN NITROGEN
BACTERIA INCORPERATE NITROGEN FOR GROWTH MEDIUM INTO NEW DNA

Grow bacteria in medium of N15 for many generations
Transferred to N14 medium for one generation
DNA = 100% hybrid DNA (1/2 light 1/2 heavy)
DNA spun in a centrifuge and formed 1 strand 1/2 way up test tube
1srt Generation divides again in N14
50% Hybrid DNA, 50% light
Spun in centrifuge and formed 2 strands, one closer to the top
1 1 1———-1
1 1 1 1
1 ———1 1———-1
1 1 1 1
1_____1 1 _____1

Question 8

Describe and explain how the structure of DNA results in accurate replication

Answer 8

semi-conservative replication
Hydrogen bonds between complementary base pairs allows strands to separate
Base sequence exposed so act as template