Chapter 3 - nucleic acids Flashcards
differences between DNA and RNA
- Deoxyribose versus ribose
- DNA is double-stranded and anti-parallel, where RNA is single-stranded
components of a nucleic acid
- 5-carbon sugar
- nitrogeneous base
- phosphate group
new nucleotides in nucleic acid are always added at the 3’ position.there is always a 3’ (diester) at one end and a 5’ (phosphate) at the other end
purines
guanine and adenine. purines have double-ringed structure (larger).
pyramidines
- cytosine
- thymine— DNA only
- uracil — RNA only
Pyramidines have single ring structure (larger)
adenine base
[placeholder: need to be able to draw the structure]
structure of ribose
[placeholder: need to be able to draw ribose in its linkages]
structure of deoxyribose
the oxygen at C-2’ is missing. Found in DNA
phosphodiester bond
linkage between a 5’ phosphate and 3’ hydroxyl (where the ends were alcohols (ester linkage). Formed through dehydration synthesis. Sort of like an ester, but a P instead of C.
Ends of DNA are always…
(start with) 5’ phosphate on one end and 3’ hydroxyl on the other
Antiparallel
Refers to alignment of DNA strands, where a 5’ phophate on one strand, means a 3’ hydroxyl on the other.
DNA’s helix structure
- Right-handed helix
- B-DNA is the common form
- Bases are held together by H-bonds (lots–making stable)
- 10 bases per turn, 3.4nm per bp, 2nm wide (can only see with electron microscope).
- All proteins interact with DNA in major groove
C-G bonds
3 H-bonds. They are relatively more stable than A-T bonds with 2 H-bonds
Watson and Crick
Discovered DNA in 1953. Linus Pauling was a helix expert competing with them. Rosalind Franklin gave a talk that showed crystallography of a helix structure. Franklin was not cited.
RNA’s secondary structure
Where RNA has folded over to create sections of helixes
Nucleoside
A base and sugar, no phosphate
