Introduction to Molecular Biology 2

Question 1

What three ways were theorised on how two strands of DNA be copied?

Answer 1

Semiconservative model

Conservative model

Dispersive model

Question 2

Describe the semiconservative model?

Answer 2

Hydrogen bonds between the strands are broken and form two sets, one with a daughter and mother strand

Question 3

Describe the conservative model?

Answer 3

Hydrogen bonds are not broken and the daughter strands are two new strands

Question 4

Describe dispersive model

Answer 4

Patchwork on new daughter strands with maternal DNA

Question 5

What model was found to be correct?

Answer 5

Semi-conservative model

Question 6

What specifies which base is to be added next?

Answer 6

Template strand

Question 7

In what direction is the growing strand in?

Answer 7

5’ to 3’

Question 8

In what direction does DNA polymerase move?

Answer 8

3’ to 5’

Question 9

How does DNA polymerase replicate the lagging strand?

Answer 9

By synthesising in short Okazaki fragments

Question 10

What is required for multiple Okazaki fragments?

Answer 10

RNA primer

Question 11

What is Werner’s syndrome caused by?

Answer 11

Very short telomeres

Question 12

What is gene repeated at the telomere?

Answer 12

TTAGG

Question 13

How is DNA at the telomere end replicated?

Answer 13

As the template strand is not long enough to fit DNA polymerase on, telomerase binds offering an additional length of RNA

This allows for DNA polymerase to complete the lagging strand

Question 14

Where is telomerase very active?

Answer 14

Stem cells

Question 15

How can errors in DNA replication be recognised?

Answer 15

Through proofreading in DNA polymerase

Question 16

What increases the risk of mutations occurring?

Answer 16

Failure of mismatch repair

Question 17

How often is there an error in DNA replication?

Answer 17

1 in every 3 genomes

Question 18

What are the different stages in PCR?

Answer 18

Heat is used to separate DNA strands

The strands are then cooled and primers are added

These primers then bind which allows DNA polymerase to replicate

Question 19

Example of PCR in clinical setting?

Answer 19

Testing for infectious agents through PCR amplification of specific infectious genes

Question 20

How can inheritance patterns be examined?

Answer 20

By using PCR you can find on which chromosome a genetic defect is on

Question 21

How is PCR used in DNA sequencing?

Answer 21

The normal deoxyribonucleoside triphosphates are added and a small amount of dideoxyribonucleoside triphosphate is used as well

The dideoxy….. is used as a stopping sequence to block further growth

In each test tube there is a different dideoxy… which will stop for on a certain base, ie ddATP, ddTTP, ddCTP and ddGTP

You then use gel electrophoresis and the lightest chain will move to the bottom

By working your way up you can then build up the targeted gene sequence

Question 22

What is Alexander disease caused by?

Answer 22

Lack of G base changing to a T

Glial fibrillary acidic protein