The Replication of DNA Flashcards
What is the meaning of semi-conservative replication?
That one strand of the new DNA comes from the original DNA molecule and one strand comes is newly synthesised (i.e. half of the original DNA was conserved)
What are the requirements for DNA replication?
- DNA Template
- Supply of DNA Nucleotides
- Supply of Energy (ATP)
- Enzymes (DNA Polymerase and Ligase)
- Primers for DNA Polymerase
Why is a DNA template required for DNA replication?
It provides the code to copy
Why is a supply of DNA nucleotides required for DNA replication?
To build the new strand of DNA
Why is a supply of energy required for DNA replication?
To provide the enzymes with energy in order to:
- Unwind the DNA
- Pair up the new nucleotides
- Join up the backbone
- Rewind the DNA spiral
Why is the enzyme DNA polymerase required for DNA replication?
- To unwind the DNA by holding the replication fork open
- Pair up the free nucleotides
Why is the enzyme ligase required for DNA replication?
To join up the fragments on the lagging strand
Why are primers for DNA polymerase required for DNA replication?
To provide a ‘starter’ for the attachment of nucleotides by DNA polymerase
What is meant by ‘directionality of DNA polymerase’?
That DNA polymerase can only add nucleotides running in one direction (from 3’ to 5’)
What is a leading strand?
The DNA strand that is added to continuously (attaching nucleotides to the 3’ end)
What is a lagging strand?
The DNA strand that can only be added to once the replication fork opens up far enough for the enzyme to lock on
What are okazaki fragments?
The DNA fragments which form on the lagging strand
What is the replication fork?
The point where the DNA double-helix is ‘unzipped’
What is a primer?
A short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing DNA polymerase to add DNA nucleotides
On long chromosomes many replication forks might be started at various points along the length of the chromosome. Why is this of benefit?
It cuts down the length of time it will take to complete replication of the whole length
