Nucleic Acids Flashcards
week 1 lecture 2
1
Q
What do nucleotides contain
A
- a nitrogenous base
- one or more phosphates
- a pentose sugar
2
Q
Describe the structure of DNA
A
- two antiparallel strands held by hydrogen bonds between bases
- has a 3’ end and a 5’ end with a sugar phosphate backbone connecting next carbon
- G-C and T-A
3
Q
What is a nucleoside
A
a nitrogenous base + sugar
eg. adenosine, cytidine
4
Q
What are the two different types of nitrogenous bases
A
purines
- double rings (A and G)
pyrimidine
- single ring ( T,U,C)
5
Q
What are nucleic acids
A
unbranched polymers made of nucleotide monomers
6
Q
How does the double helix and structure of DNA make is stable
A
- separating of backbones to avoid electrostatic repulsion and allow exposure to the solvent
- bases form mutually stabilising hydrogen bonds
- stacking of bases maximises ring interaction
(aromatic rings of bases are attracted and hydrophobic interactions drive bases inside the helix)
7
Q
Why are there major and minor groves in DNA
A
To allow DNA code to be read without unwinding the structure. Sequence specific DNA binding proteins read the chemical information in the groves
8
Q
What is the structure of RNA
A
- an unbranched polymer of ribonucleotides
- predominantly single-stranded
- has uracil not thymine as no biosynthetic pathway in cells to produce thymidine ribonucleotide and thymine is more energetically costly
- RNA is more reactive from OH group instead of H
- RNA in solution will break itself down as intrinsically less stable
9
Q
What happens when uracil is in DNA
A
- cytosine can undergo deamination and become uracil when H2O is added and NH2 is taken away
- this can be fixed as the DNA repair process recognises uracil and removes it as it is not normally present in DNA
