DNA structure Flashcards
Nucelotides consist of
- nitrogenous base
- pentose sugar
- one of more phosphate groups
Nuceloside
nitrogenous base+sugar
What are the two families of nitrogenous bases?
- Pyrimidine
- Purines
Phosphodiester linkage
sugar-phosphate backbone and nitrogenous base (appendages)
Rosalind Franklin
proposed 2 strands with sugar-phosphate backbone and bases on interior
Watson and Crick
built models of a double helix to conform to the X- rays and chemistry of DNA
Structure of DNA molecules
- Double helix: 2 polynucleotides spiraling around imaginary axis
- Antiparallel: backbone runs in opposite 5’ to 3’ directions
- Complementary base pairing: H bonds A-T, C-G
Double helix similarity with screw
right-handed chirality; twist moves away from helix
helical pitch; van der waal interactions; hydrogen bonds
Structure of RNA molecules
Single-stranded; variable in form (mRNA;tRNA; rRNA; sRNA); complementary base pairing C-G, A-U
5’ end
phosphate group
3’ end
sugar
DNA is more than just a macromolecule
“molecules of inheritance” and “life’s operating instructions”
heredity, traits
genetic material contains genes
Frederick Griffith
Discovered DNA can confer to new traits
Discovered bacterial transformation; transmitted cell to cell
Alfred Hershey and Martha Chase
Discovered DNA is component of bacteriophage that enters cells (genetic material)
Erwin Chargraff
Discovered DNA composition varies from one species to the next - diversity made DNA more credible candidate for genetic material
