DNA Replication Flashcards
(20 cards)
what is needed to make DNA (7)
- the progressive addition of new nucleotides
- a starting point for new nucleotide addition
- unwinding of helical double stranded DNA to give 2 parental strands
- release of tension generated by unwinding the DNA helix
- prevention of unwound double stranded helical DNA from reforming and to protect it
- removes RNA primer and fills gaps with DNA nucleotides
- joining of ends of newly synthesised fragment together - lagging and leading within and between bulbs
which way is DNA and RNA synthesised
5’ to 3’ direction
which way does the parental strand run from
3’ to 5’ direction
how many chromosomes do humans have
23 pairs - 46 chromosomes
what is ori
the origins of replication (multiple places)
what does bidirectional mean in DNA replication
starts replicating on both sides of the ori (opposite directions)
what is the role of primase enzyme in DNA replication (DNA polymerase III)
enzyme that synthesises a new DNA strand by adding nucleotides complementary to the parental template strand
needs an OH group onto which the phosphate group of the incoming nucleotide can be attached
what is the role of helicase in DNA replication
unwinding the double helical strand of DNA into 2 2 parental strands
what is the role of topoisomerase in DNA replication
release the tension that is generated by the unwinding of DNA helix
what is the role of a single-stranded DNA binding protein in DNA replication
preventing the unwounded strand of DNA from reforming and protecting it
what is the role of DNA polymerase I in DNA replication
has 2 activities
1. removes RNA primers which is an endonuclease enzyme that recognises DNA:RNA hybrid and degrades the RNA part
2. fills in the gap with DNA nucleotides by synthesises DNA by adding nucleotides complementary to the parental DNA template of the lagging strand
what is the role of DNA ligase in DNA replication
- joins the newly synthesised Ozaki fragments together (creates phosphodiester bonds), once the RNA primers have been removed and replaced by DNA nucleotides
- joins the newly synthesised fragments from the multiple replication bubbles - including the leading strands
what is a leading strand
continuously synthesised in its 5’ to 3’ direction
what is a lagging strand
discontinuously synthesised in its 3’-5’ direction as Okazaki fragments
what is a polymerase chain reaction (PCR)
a laboratory technique used to make millions to billions of copies of a particular section of DNA from a very small original amount, which can be studied in greater detail
when can errors in DNA replication appear
- during replication
- after replication
how are DNA errors repaired during replication
- DNA pol III has a replication has a very low base-pairs replication error rate
- DNA pol III has a proofreading mechanism by checking newly inserted nucleotide bases against the template
- these bases can be removed by a 3’-5’ exonuclease activity of DNA pol III
what factors causes errors to appear after DNA replication
- incorrectly inserted bases are nor corrected by DNA pol III
- radiation damage
- chemical modification of bases (natural or chemical)
how are DNA errors repaired after replication
damaged bases are removed by an endonuclease
why is it important to repair DNA errors/damage
if errors are not corrected it becomes apart of the DNA sequence and can cause permanent damage such as mutation and DNA damage
