Introduction to Molecular Biology 2 Flashcards
What three ways were theorised on how two strands of DNA be copied?
Semiconservative model
Conservative model
Dispersive model
Describe the semiconservative model?
Hydrogen bonds between the strands are broken and form two sets, one with a daughter and mother strand
Describe the conservative model?
Hydrogen bonds are not broken and the daughter strands are two new strands
Describe dispersive model
Patchwork on new daughter strands with maternal DNA
What model was found to be correct?
Semi-conservative model
What specifies which base is to be added next?
Template strand
In what direction is the growing strand in?
5’ to 3’
In what direction does DNA polymerase move?
3’ to 5’
How does DNA polymerase replicate the lagging strand?
By synthesising in short Okazaki fragments
What is required for multiple Okazaki fragments?
RNA primer
What is Werner’s syndrome caused by?
Very short telomeres
What is gene repeated at the telomere?
TTAGG
How is DNA at the telomere end replicated?
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
Where is telomerase very active?
Stem cells
How can errors in DNA replication be recognised?
Through proofreading in DNA polymerase
What increases the risk of mutations occurring?
Failure of mismatch repair
How often is there an error in DNA replication?
1 in every 3 genomes
What are the different stages in PCR?
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
Example of PCR in clinical setting?
Testing for infectious agents through PCR amplification of specific infectious genes
How can inheritance patterns be examined?
By using PCR you can find on which chromosome a genetic defect is on
How is PCR used in DNA sequencing?
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
What is Alexander disease caused by?
Lack of G base changing to a T
Glial fibrillary acidic protein
