DNA replication Flashcards
Which bases are involved in DNA?
ACTG
What type of structure is DNA?
Double helix structure
Where are bases joined to in DNA?
Joined from 3’ to 5’ OH’s of the sugar by a phosphate group
What are genes?
The chunks of the DNA code when it has been split
What do genes control?
Much of who we are, eg, height and eye colour
How many nucleotides are in the complete human genome?
3 billion
How many genes are in the complete human genome?
31,000
Which bases pair together?
Thymine and adenine
Cytosine and guanine
How many hydrogens between thymine and adenine?
2
How many hydrogens between cytosine and guanine?
3
What is the base pairing always like?
Purine to pyrimidine
Which bases are purines?
Adenine
Guanine
Which bases are pyrimidine?
Thymine
Cytosine
What does the base pairing mean?
The DNA strands are complimentary to each other
When the double stranded DNA splits, was are the two strands formed?
Leading strand
Lagging strand
Why does DNA replicate?
When a cell divides each cell needs a full set/copy of the DNA
What type of replication is DNA replication? What does this mean?
Semi-conservative
The strands formed are half new and half old
What was Watson and Cricks experiment?
They had a N15 and an N14 isotopes in bacteria
Then the first generation produced contained half of each isotope
What does DNA helices do?
Unwinds the DNA strand
What does DNA polymerase do?
Makes new DNA strand
What does RNA primate do?
Makes RNA primers for the lagging strand
What does RNase H do?
Removes RNA primers
What does DNA ligase do?
Joins the Okazaki fragments to create one continuous strand
What does DNA polymerase catalyse?
the step by step addition of deoxyribonucleotide units to a growing DNA chain
Which 4 activated precursors does DNA polymerase need to work?
dATP
dGTP
dTTP
dCTP + Mg2+
Where does DNA polymerase add the deoxyribonucleotides to ?
the 3’-hydroxyl group of a DNA chain called the primer
What type of reaction is the one involving DNA polymerase?
Nucleophilic attack of the 3’OH terminus of the primer DNA on the innermost phosphorus atom of a deoxynucleoside triphosphate
What provides the energy for the DNA polymerase chain elongation reaction?
The nucleophilic attack releases a diphosphate unit which Is hydrolysed by inorganic pyrophosphatase
How often does DNA polymerase make a mistake?
Once every 10,000,000 base pairs
What does PCR do?
Amplifies specific DNA sequences
What are the three steps of PCR?
Denaturation
Annealing
Elongation
What happens in denaturation?
Strand separation
Two strands of DNA are separated by heating
What happens during annealing?
Hybridisation of primers
Short strands of DNA flanking the 3’ ends of both strands of DNA are hybridised to the sequences
What happens during elongation?
DNA synthesis
DNA polymerase is added and elongation of both primers occurs
