DNA Structure and Replication Flashcards
Which direction does replication occur?
5’ - 3’
what is a nucelotide made out of
base sugar phosphate
what is a nucleoside made out of
base sugar
what are the purine bases
adenine and guanine
what are the pyramiding bases
thymine cytosine
which base pairs have 2 bonds and which have 3
A-T have 2 bonds
C-G have 3 bonds
what is the role of DNA helicase
forms replication fork by unwinding the DNA at the start of replication
What is the role of DNA polymerase 2
joins nucleotides onto RNA primer
What enzyme replaces RNA with DNA
DNA polymerase 1
Which enzyme is used in prokaryotes for replication
DNA polymerase 3
what is the role of DNA ligase
sales gaps in okazaki fragments
what is the error rate in base pairing
1 in 10^9 bases
GC to AT mutations are caused by?
EMS alkylates
what is the energy driver of replication
pyrophosphate release
list three key features of DNA structure
double stranded, antiparallel chains of nucleotides. there is complimentary base pairing - DNA is a double helix
what is the name of the bonds that hold the backbone together
phosphodiester bonds between sugar phosphates
give three differences differences between DNA, RNA structure
dna is double stranded
dna has deoxyribose
dna contains thymine
what is the role of DNA primase
lays down a short strand of RNA to act as a primer for DNA synthesis - this is an RNA polymerase
what do single stranded binding proteins do
stabilising the replication fork so that the strands don’t come back together
what are the requirements for DNA synthesis by DNA polymerase
template, free 3’ OH, all four dNTP
what are okazaki fragments
the short fragments of DNA synthesised on the lagging strand of DNA which contain an RNA primer - the primer is then removed by DNA polymerase 1 and the fragments are joined by DNA ligase
in what sort of cell does a mutation have to occur in order to me inherited
mutation in the gametes
what is the function of the enzyme uracil N glycosylase
cuts uracil from the DNA which arises from the deamination of cytosine - this can cause a C to T mutation
what is a polymorphism
a sequence variation that occurs in at least 1% of the population
what is SNP
single nucleotide polymorphism
how does mature mRNA reach the cytoplasm
through nuclear pores
to which end of the tRNA module is the amino acid attached
3’
name three antibiotics that target prokaryotic ribosomes
tetracycline, streptomycin and chloramphenicol
in which organelle does most post translational modification of secreted
golgi complex
name three modifications of mRNA in eukaryotes
5’ cap, poly A tail, splicing out introns
