DNA replication Flashcards
What is semi-conservative DNA replication?
Where 2 strands of DNA molecule separate + each strand acts as template for new DNA molecule
When is DNA replicated?
Before cell division starts
What is the process of breaking up the strands?
- Portion of DNA about to undergo replication
- 2 strands of DNA separate/unzip by DNA helicase enzyme. DNA helix unwinds + hydrogen bonds between bases break
3.
What is the process of joining up strands?
- Free nucleotides are attracted to their complimentary bases - no enzymes needed for this, hydrogen bonds form naturally
- Nucleotides line up, then joined by DNA polymerase enzyme
- All nucleotides join to form complete polynucleotide chain using DNA polymerase. 2 identical strands of DNA formed, zips back together
What is each new DNA molecule made up of?
Original DNA strand + newly synthesised strand
What is the name of the process that makes up new DNA molecules? (step 5)
Semi-conservative replication
What experiments show DNA replication? What does it prove?
Meselson + Stahl Experiments, 1958 - proves DNA replication is semi-conservative
What is continuous + discontinuous replication?
Addition of new DNA nucleotides to eachother via condensation reaction, forming phosphodiester bond
Where does the new phosphodiester bond form?
Between 3’ OH group of 1 nucleotide + OH group of 5’ phosphate group of adjacent nucleotide
What direction can new nucleotides be added to an existing DNA strand?
From 5’ to 3’ direction of new strand
How does this occur on leading strand?
Continuously as DNA is unzipped by DNA helicase
Why cant it occur continuously on the lagging strand?
Its unzipped in opposite direction - 2 strands of DNA molecule are antiparallel
What is a mutation?
Where base pairing between template strand + newly synthesised strand dont follow base pairing rule
Mutation can occur spontaneously + randomly
