DNA Replication Flashcards
DNA has _ bp/turn and each turn is _ nm long
10, 3.4
Semi-conservative nature of DNA replication
After one round of DNA replication, each DNA molecule contains 1 parental and 1 newly synthesized strand
Who demonstrated that the semi-conservative model
Meselson and Stahl
How did meselson and stahl demonstrate the semi-conservative model
Used CsCl equilibrium density gradient centrifugation to separate double-stranded DNA molecules of different densities.
Heavy DNA with N15 sediments further down the CsCl grad
Light DNA with N14 near the top of CsCl gradient
Several rounds of DNA replication demonstrated that the heavy nitrogen tagging allowed separation of 2 bands of DNA in the centrifuge- one was comprised of conserved and new DNA and the other entirely newly synthesized DNA
Theta Replication
Occurs is most circular DNA, is bidirectional from the origin.
As forks migrate around the circle, they meet up and have formed 2 complete new cirlcles
Rolling circle replication
A specialized form of replication that occurs in F factor and some viruses
Unidirectional, initiated by a nick in DNA and begins at the 3’ end of the broken strand, displacing 5’ end and forcing out a strand that will be taken up by another cell.
Linear chromosome replication
occurs in linear chromosomes of eukaryotic cell
Bidirectional from point of origin, multiple points of origin
along chromosomes
DNA replication requires?
Mg2+, DNA dependent DNA polymerase, 4 deoxyribonucleoside triphospahetes (dNTPs), a template strand to be copied and an RNA primer.
dNTP is like a regular nucleotide but with 4 phosphates groups instead of 1?
True or false
FALSE
RNA primer provides 3’-OH end to initiate DNA synthesis by DNA polymerase
True or false?
TRUE
DNA is always synthesized in the 5’ to 3’ direction, strands are complementary & antiparallel
True or false?
TRUE
DNA strands are held together by H-bonds between bases (3 between C and G, 2 for A and T)
True or false?
TRUE
