DNA replication specific to eukaryotes
comparison to prokaryotes
much larger amount of DNA in euk.
more complex DNA polymerases (#15)
DNA is associated with histones
the presence of telomeres (b/c euk. DNA is not circular)
there are multiple origins of replication b/c there is so much DNA to replicate (during S phase)
DNA polymerase (pol) delta: is the main DNA polymerase, it has 3' to 5' exonuclease activity (proofreading)
nucleosomes and replication
they are displaced as the replication fork advances
histones remain loosely associated with the parental DNA
new histones synthesized simultaneously with DNA replication
they rapidly reform behind the replcation fork
Telomeres
short G-rich DNA sequence at the ends of chromosomes
in humans (TTAGGG)n with ~1000 copies/telomere
prevent the loss of terminal sequences during replication
protect the chr ends from fusion, and from being recognized as broken DNA and degraded
telomerase
a ribonucleoprotein complex (RNA + protein)
reverse transcripase: makes DNA using RNA as a template (this is the only place this happens in human genome)
adds short DNA repeats to the 3' ends of chromosomes
forms a T-loop which protect the end of the chromosome