CP 11 DNA Structure / Replication Flashcards
what is Griffiths experiment
Substance derived from killed infective pneumonia bacteria could transform a non infective living pneumonia bacteria to the infective type
what are the 2 strains in griffiths experiment
Smooth (S) = Virulent, causes pneumonia killing mice
Rough (R) = Nonvirulent = does not kill mive
what are the steps to griffiths experiment+what happens to the mice
- Mice injected with live S cells (mice die)
- Mice injected with live R cells (mice live)
- Mice injected with heat-killed S cells (mice live)
- Mice injected with heat-killed S cells + live R cells (mice die)
why did the mice die when mixing live R strain and killed S strain ?
Living R bacteria had acquired traits from dead S bacteria transformed into virulent S cells
what does each nucleotide contain of
1 - 5 carbon sugar
1 phosphate grp
1 nitrogenous base
what is chargaffs rule
Number of purines equals number of pyrimidines
what are the purines and pyrimidines
pur = AG
pyr = TC
TF polynucleotide chain does not have polarity
F, it does
in the polynucleotide chain where does the phosphate and hydroxyl group bind
P = 5’ end
H = 3’ end
how does x-ray diffraction work
- X-ray beam directed at molecule in form of regular solid (ideally a crystal)
- Positions of atoms in molecule deduced from diffraction, patterns produced on photographic film
what is the basic structure of the double helix
Two polynucleotide chains (sugar phosphate backbones) twist around each other in right-handed way, pairs of bases fill the central space
what are the 3 models of DNA replication
- Semiconservative
- Conservatice replication
- Dispersive replcation
what are the steps to semiconservative replication
- Hydrogen bonds between two strands break
- Two strands unwind and separate
- Each strand acts as template for synthesis of new, complementary strand
- Each new double helix has one old strand (parental DNA) and one new strand
what are the steps to conservative replication
- parental DNA strands unwind
- each is template for synthesis of new strand
- after replication, the 2 parental and 2 resulting strands pair up again
- resulting helicases are 2 old strands and 2 new strands
what are the steps to dispersive replication
- double helix unwinds
- both strands of DNA are chopped up into pieces
- pieces are then replicated individually, in each piece, new DNA nucleotides pair with the old ones
- newly synthesized DNA fragments and the original DNA fragments are randomly interspersed and reassemble into two complete DNA molecules
what does DNA polymerase use for DNA replication
4 dNTP’s (deoxyribonucleoside triphosphates)
dATP, dGTP, dCTP, dTTP
which direction does DNA polymerase assemble nucleotide chains
5’–>3’ (daughter strand)
which way it the DNA template read
3’–>5’ (parental strand)
what is the structure of a DNA polymerase
- Hand shaped
- Template DNA lies over “palm” in groove formed by “fingers” and “thumb”
how do the DNA polymerase,3’-OH, new and template strand all work together
Template strand and 3′-OH of new strand meet at active site for DNA synthesis polymerization
reaction, located in palm domain
what is the sliding DNA clamp
Protein that encircles DNA and attaches to rear of DNA polymerase, Tethers DNA polymerase to
template strand and increases rate of DNA synthesis
What are Single-stranded binding proteins (SSBs) used for
Coat exposed single-stranded DNA segments
to Keep them from pairing
what does Topoisomerase do
cuts and rejoins DNA to prevent twisting as DNA unwinds
