DNA Replication Flashcards
What are the 3 possible replication patterns of DNA?
Semiconservative replication
Conservative replication
Dispersive replication
Semiconservative replication
Would produce molecules with both old and new DNA, but each molecule would contain one complete old strand and one complete new one
Conservative replication
would preserve the original molecule and generate an entirely new molecule
Dispersive replication
would produce two molecules with old and new DNA interspersed along each strand
what are the 2 steps of semiconservative DNA replication?
double helix unwound into 2 strands
new nucleotides form complementary base pairs and covalently link together
how does replication begin
binding of large protein comoplex to specific site on DNA molecule
origin of replication
found on all chromosomes- pre replication complex binds
what is the third step in DNA replication
DNA is unwound and replication proceeds in both directions around circle to form two replication forks
what does DNA replication have to begin with?
primer- short, started strand of RNA
what is the 5th step in DNA replication
DNA polymerase elongated a polynucleotide strand by covalently linking new nucleotides to preexisting strand
what synthesizes the primer? How many nucleotides at a time?
primase, 1
what happens after the primer is synthesized?
DNA polymerase adds nucleotides to 3’ end of primer
after the nucleotides are added to the 3’ end of the primer, what happens?
RNA primer degrades and when DNA is replicated, only DNA left
describe DNA polymerases
large and shaped like right hand
how do proteins assist with DNA polymerization
unwind and separate DNA strands held together by hydrogen bonds and van der waals
DNA helicase
uses energy from ATP hydrolysis to unwind and separate strand
single strand binding proteins
bind to unwound strands to keep them from reassociating into a double helix
DNA at replication fork
DNA unwinds to expose bases
Leading and lagging strands
leading strand
grow continuously at 3’ end (forward)
lagging strand
3’ end gets farther from fork and gap forms (backward)
Synthesized by Okazaki fragments
DNA ligase
catalysts formation of bond for lagging strand
what are the parts of DNA synthesis
DNA helicase, 2 polymerases, primase, ligase, proteins
DNA polymerases are (blank)
processive
processive
catalyze the formation of many phosphodiester linkages each time they bind to a DNA molecule
sliding DNA clamp
stabalizes DNA polymerase
telomeres
repetitive sequences at the ends of chromosomes
bind protein to prevent recognition of chromosome breaks
telomerase
catalyzes the addition of any lost telomeric sequences in these cells
