DNA and RNA Structure Flashcards
Who discovered nucleic acid?
Freidrich Miescher
He saw it was concentrated inside the nucleus but did not establish its composition.
What 3 characteristics should genetic material have?
1: Sustain life (contain info about structure, function, growth and reproduction in a stable form)
2: Replicate accurately
3: change in order to generate variation
Griffiths transformation experiment
Injected 2 strains of bacteria into mice: S and R
Living S cell = mouse died
Living R cells = mouse healthy
Heat killed S cells = mouse healthy
Mixture of heat killed S cells and living R cells = mouse died
Concluded that there is some form of transferable genetic material. Living R cells had been transformed into S cells.
Avery’s transformation experiments
Prepared cultures containing heat killed s strain
Treated the solution with either DNase, RNase or protease.
Introduced living R cells to the culture.
S strain only failed to grow in the DNase culture (no DNA = no transformation.
Hershey - Chase bacteriophage experiments
Viruses were grown in 2 mediums - 1 with sulfur & 1 with phosphorus.
Viruses infected a bacterium and the virus and bacteria was separated via centrifugation.
Bacterial pellet was only radioactive when in phosphorus medium.
Effect of UV light on genetic material
UV light is known to induce mutations. This was studied by subjecting fruit flies to different wavelengths of UV light, producing mutations.
What components are in DNA/ RNA?
Pentose sugar (deoxyribose/ribose)
Nitrogenous base (A,G,T,C,U)
Up to 3 phosphate groups
Chargaff’s Rule
50% of bases are purines, 50% are pyrimidines in every DNA molecule. A=T and C=G.
Nucleotides
Linked together by phosphodiester bonds (covalent) between the phosphate group and the 3’ carbon.
dNTPs (deoxyribonucleotide triphosphate)
dNTPs are free nucleotides that have 3 phosphate groups at the 5’ carbon.
DNA model characteristics- Francis Crick & James Watson
2 polynucleotide anti parallel chains in a right handed double helix. Hydrophilic sugar phosphate backbone with unequal spacing between. Bases are perpendicular to the axis. Base pairs are 0.34nm apart.
Three different forms of DNA
A-DNA
B-DNA
Z-DNA
A-DNA
Right handed helix
Short and wide
Narrow and deep major groove.
Shallow minor groove.
Low humidity conditions.
B-DNA
Right handed helix
Thin and long
Wide major groove.
Narrow minor groove.
High humidity conditions.
Z-DNA
Left handed helix with a zig zag sugar phosphate backbone.
Thin and long.
Deep minor groove.
Occurs temporarily during transcription.
