Lecture 7 DNA Replication Flashcards
What does semiconservative mean?
Both daughter helices contain one new strand and one old template strand
What does DNA polymerase do?
DNA polymerase reads a template strand and covalently links de-oxyribonucleotides (dNTPs) to create a new DNA strand
What does a nucleotide need to have to enable the next nucleotide to be added?
It needs three -OH groups to be able to elongate the strand
What does hydrolysis of pyrophosphate do?
It releases energy that enables a polymerase to move along a template strand
What does Pol alpha do?
Acts as a primase and synthesises RNA primers at replication form origins (for the leading and lagging strand) and during lagging strand synthesis (Okazaki fragments)
What does a primase (subunit) do?
Enables the start of genomic DNA replication by creating RNA “primers” that a DNA polymerase can extend
What is the role of the clamp proteins?
Secures DNA polymerases to a template strand
What is the role of a helicase?
Unwinds DNA duplex into a single stranded DNA
Lagging strand synthesis is….
Discontinuous (made up of a number of short DNA molecules)
Short DNA fragments found in the lagging strand are called…
Okazaki fragments
The final fusing of Ozazaki fragments is carried out by….
DNA ligase to form a single long molecule
What is a replication origin?
Genomic regions at which DNA replication starts
What happens when replication forks meet?
They merge together in a process (little is understood about this process however)
What does TNR mean?
Tri-nucleotide repeat disease
Why do TNRs appear?
Results from a form of replication error e.g polymerase ‘slippage’.
Typically occurs where there are short tandem repeating sequences. Repeats increase the chance that a mistake is made in aligning the growing DNA strand with its template strand
