DNA replication - 12 Flashcards
What enzyme pulls DNA strands apart
Helicase
What does Ligase do
Joins together Okazaki fragments and replication bubbles.
What enzyme cuts and sticks back together DNA strands
Topoisomerase
What does DNA polymerase ||| do
Synthesises DNA (From corresponding bases on template strand)
What does the enzyme primase do
Lays down a staring RNA primer for polymerisation
What does SSBP do
Prevents strands from degrading
Stops strands from binding together
What does DNA polymerase | do
Replaces RNA with DNA nucleotides
What are Okazaki fragments
The separate fragments that lagging strand creates
Why is there a lagging and a leading strand
DNA can only synthesise from 5’ - 3’. Synthesis starts from the origin of replication on the leading strand and is continuous. The lagging strand must be synthesised in fragments and is discontinuous
What are the two ways errors in DNA are corrected
Exonuclease
Endonuclease
How are mistakes detected and corrected in Exonuclease
During synthesis (replication) DNA polymerase ||| checks as it lays down base pairs and if it detects errors it will try to correct them.
How are mistakes detected and corrected in Endonuclease
After synthesis (replication) An enzyme will remove a chunk around and including the error and polymerase will fill in the gap.
Why is it important to fix DNA errors
If errors aren’t fixed then mutations occur and are passed on to daughter cells. This could result in the daughter cell, and any other cells it produces, to not be able to fulfil their function
What is the difference between PCR and DNA replication
PCR has a DNA primer, has two continuous strands and only has one enzyme
What is ‘in vitro’ replication (PCR)
Method of making multiple copies of DNA so their is enough material to work with. Only copies a targeted region and utilises cycles of heating and cooling. (For PCR)
