genetics 1 Flashcards
what are purines
DNA bases
what are pyrimidines
RNA bases
how are sugars attached to purines and pyrimidines
C-1 of sugar attached to N-9 of purine and N-1 of pyrimidines
where is the phosphoryl group attached too
5’ carbon atom of the sugar
where is the free hydroxyl group attached too
3’ carbon of sugar
what is the structure of DNA
- antiparallel polynucleotide strands
- right handed helix
- sugar-phosphate backbone outside
- bases inside
what do genes contain
exons - encoding
introns - connecting
where are the major and minor groves
major - when helix is away from you
minor - when helix is towards you
how are introns removed
splice out by spliceosomes to generate mature messenger RNA
what do single stranded DNA binding proteins do
cooperative protein binding straightens region of the chain so DNA polymerase can work
where does cytosine methylation take place
on DNA at CG motifs
how does cytosine methylation work
- when DNA replicates only the original strands have methyl groups attached
- one side not recognised by maintenance methylase
- methyl group attached to CG motif
what causes damage to DNA
- errors in DNA replication
- mutagens
- errors in DNA repair
what is a transition mutation
goes from one purine to another or one pyrimidine to another
what is a transverse mutation
goes from a purine to a pyrimidine or vice versa
what does deamination do
thymine and adenine base pair
what does oxidative damage do to DNA
- adds oh to thymine and guanine
- blocks DNA replication and transcription
what does depurination do to DNA
N-glycosidic bonds are cleaved to release a corresponding adenine or guanine
what does alkylating agents do to DNA
adds methyl groups - blocks DNA replication and transcription
what does bulky adducts do to DNA
when binding results in abnormal DNA replication
what does base analogues do to DNA
molecules which are substituted for bases of DNA
what does intercalating agents do to DNA
intercalated molecule attaches to DNA helix causing base insertions and deletions
what does uv light do to DNA
- formation of dimers
- creates photoproducts
- generates free radicals
- strand breaks
- blocks DNA replication and transcription
what does ionising radiation do to DNA
- causes a double strand break
- various mutations due to strand break repair and oxidative damage
