L16A+B DNA Replication Flashcards
What is meant by replication
Process where DNA makes a copy of itself each time the cell divides
Occurs in S phase of interphase
Rules of DNA replication
Semi conservative
Begins at multiple origins and proceeds bidirectionally
Exhibits polarity(proceeds in a 5’to3’ direction
Very accurate
How far are origins spaced
30,000 to 300,000 base pairs apart
How are origins identified
By origin recognition complex proteins
ORC
What are steps of DNA replication
1-DNA unwinding 2-DNA primer synthesis 3-DNA polymerization 4-degrading RNA primers 5-Ligation
Enzyme that breaks down bonds between nit bases
Helicase
What prevents unwound DNA from rewinding back
Single stranded DNA binding proteins
What prevents super coiling of DNA
DNA topoisomerases
Unwinding of DNA causes formation of structure called…
Replication fork
Enzyme responsible for replication
DNA polymerase
What does DNA polymerase require to work
RNA primer
How are RNA primers synthesized
By RNA primase
Leading strand
5’»»3’ continuously away from origin
Lagging strand
5’> 3’ towards the origin
What are Okazaki fragments
Short fragments of DNA that are appx 150 base pairs long
Types of DNA polymerases
DNA poly a priming and initial synthesis DNA poly B DNA repair DNA poly y mtdna replication DNA poly delta lagging strand synthesis DNA poly E leading strand synthesis
How are RNA primers removed
5’»»>3’ exonuclease
And gap filled by DNA polymerase
What is ligation
Creation of phosphodiester bond between individual DNA fragments so that whole strand becomes one continuous strand
Enzyme: DNA ligase
How do diff steps of replication target anti cancer and anti microbial agents
1.incorporate DNA to interfere with chain elongation and induce defective ligation of newly synthesized DNA (antiviral: acyclovir against herpes)
2-inhibit topoisomerase in cancer cells and in bacterial cells(quinolone antibiotics)
What is proof reading
Process in which there is a cont check on newly inserted nucleotides
Base pair mismatch occurs at a freq of 1 per 10,000 nucleotides
What enzymes proof read
DNA poly 1 and 3
Function of telomeres
Maintain structural integrity of chromosome and prevent attack by nucleases and allow repair systems to distinguish a true end from a break in dsDNA
Non coding hexameric sequence is..
AGGGTT
What is telomerase
Complex contains a protein that acts as a reverse transcriptase and a short RNA template to synthesize tandemly repeating base sequences
How can HIV and COVID replicate inside body
They have reverse transcriptase which they use inside the human body to reversely transcribe the RNA (in their cells) to DNA and start replication
