Lec 15 DNA Replication & Repair Flashcards
DNA replication
How does base pairing work
both strands used as templates
semiconservative
DNA replication origins
the positions at which the double stranded DNA is first open for replication. what is its span?
100 base pairs
DNA replication origins
the positions at which the double stranded DNA is first open for replication. what type of proteins do sequences attract?
initiator proteins
DNA replication origins
the positions at which the double stranded DNA is first open for replication. What type of sequences do they prefer and why
sequences with fewer hydrogen bonds and easy to open
DNA replication origins
the positions at which the double stranded DNA is first open for replication. at which base pairs?
often A-T rich stretches of DNA
Does eukaryotes or prokaryotes have multiple replication origins and how many?
Multiple replication origins in eukaryotes
10,000 in human genomes but only one in bacteria
Explain replication forks
two replication forks are formed at each replication origin
move in both directions
how fast are replication forks
move at a rate of 1000 bp/sec in bacteria and 100 bp/sec in human
Which strand grows continuously
leading strand
which strand grows discontinuously and what is this called?
lagging strand
Okazaki fragments
What does helicase do?
unzips the double helix ahead
what does single strand DNA binding protein do
prevent DNA from re-forming base pairs
what do DNA primase do and how long
make primers (10 bases long) for DNA replication
what does DNA polymerase (3) do
adds nucleotides to the 3’ end of a growing DNA
What direction does DNA synthesis go
goes unidirectionally (5’->3’)
what does DNA polymerase 1 do
replaces the RNA primers with DNA
what does DNA ligase do
joins the Okazaki fragments
what are the ends of chromosomes called
telomeres
Replication at chromosome ends
telomers contain what repetitive base pair?
contain repetitive 6 base pair DNA sequence which is TTAGGG
how long are telomeres
10-15 kb long
when do telomeres become shorter
after each DNA replication
What do telomerase complex consist of and what do they do?
Telomerase complex consists of reverse transcriptase and telomere RNA which can add multiple copies of the repeats to the ends and slow down shortening of telomere
If telomerase complex activity is low what does it result in?
aged cells
If telomerase complex activity is high, what does it result in?
cancer cells
