Biochemistry of nucleic acids Flashcards
what is the central dogma
flow of information from Dan towards protein
what does the DNA nucleotide sequence determine
the amino acid sequences of polypeptide chains
what is a nucleoside
base and sugar
what is a nucleotide
nucleoside and phosphate group(s)
what atom is on the 2’ of deoxyribose
H
what functional group is on the 2’ of ribose
OH
what functional group is always found on the 3’ carbon
OH
Which molecules are purines
adenine
guanine
how many rings do purines have
2
what bases are pyrimidines
uracil
thymine
cytosine
how many rings do pyridines have
1
what direction does the bond between 2 Dan/rna molecules form
5’ to 3’
what functional group allows bonds to form between bases
free 3’ hydroxyl group
which bond releases high energy when broken
bond between 1st and 2nd phosphate
why can chain only grow in 1 direction
single phosphate group doesn’t have the energy to form more bonds
which end are free nucleotides added to
3’
why do DNA strands run in antiparallel directions
bonds can only be formed in 1 direction
how do nucleotide analogues stop the DNA chain from growing
drug molecule bonds to 3’
molecule doesn’t contain an OH group for next phosphate to attach to
what makes ZDV (nucleotide analogue) drugs so effective against viruses
viral reverse transcriptase has a higher affinity for ZDV (drug molecule) than human DNA
why is each DNA strand semi-conservative
each strand forms template for creation of next strand
what enzymes catalyses DNA replication
DNA polymerase
what are origins of replication
replication bubbles that start at the same time at several points and move in both directions
how is DNA replicated for the lagging strand
Okazaki fragments
how is DNA replicated on the leading strand
continuously
How does DNA polymerase proofread and repair mismatched DNA
exonuclease activity
removes incorrect nucleotide
improves error rate of mutation
What enzyme is needed to unwind the double helix
helicase
What is required before bases can be added to the copying strand
RNA primer
what synthesises an RNA primer
primase
