DNA Flashcards
Which are purines and which pyrimidine
A and G are purine so 2 rings
T and C are pyrimidine with 1 ring
What bonds between nucleotides
phosphodiester
What is on 5’ end and what on the 3’ end
5’ is phosphate
3’ is hydroxyl
what are the hydrogen bonds between bases
C and G = 2
T and A = 1
What is the hershey case experiment
grow virus in 2 different broths one rich in radioactive phosphate(in DNA) one radioactive sulfur (in proteins)
viruses then allowed to infect E.coli and then centrifuged
pellet contains the bacteria, supernatant virus
Bacterial pellet was radioactive with phosphate not sulphur proving that the DNA was inserted by the virus not the protein so the DNA contains the genetic material
What direction doen DNA polymerase work
adds new sugar ti backbone at 3’ end. only synthesises from 5’ to 3’
What happens to the lagging strand
okazaki fragments so not continuous replication. Primers are removed ribonuclease H and polymerase recognises the gaps and fills in
What is transcription
RNA polymerase binds to primer region and single strand mRNA is synthesised
what is the role of promoter
activity of the promoter determines how much of the protein is produced. It is unidirectional
Ways to protest mRNA
introns spliced out
poly A tail added (AAAAAA)
RNA cap
What is the transcriptome
section of genome to be transcribed to RNA
heterochromatin and euchromatin
hetero is inactive transcriptionally dark and dense but euchromatin is loose and active so RNA polymerase gets in
Centromere ?
repetive DNA sequence where spindles attach in cell division
Telomere ?
soecialised DNA sequence at ends of linear chromosome that maintain integrity maintained by telomerase
origin of replication ?
where replication starts not at the ends but in the middle
chemical Mutation
EMS and ENU are alkylating agents covalently bind to modify DNA single base pair change
Xray mutation cause?
induce breakdown of DNA backbone so lose fragments
UV mutation cause?
causes thymine to covalently bond to each other causing it to be read incorrectly
process of translation?
tRNA binds to specific complementary codon, peptide bonds form between amino acids that are joint to tRNA on large subunit
stop codon causes release factor to bind, end of peptide
role of large and small subunit?
large : peptide bond formation
small: decoding mRNA
what does the location of the ribosome mean
if on ER then it is fro secretion, if free floating it is for local use only
what is the N and C terminus?
N is with the amine group
C is end with carboxyl
how is a peptide bond formed?
a condensation reaction, catalysed by peptide transferase
What affect does urea have on protein?
denatures it, if removed it reverts back
What is the quaternary structure?
when 2 subunits bind to form a dimer, can be identical - homotetramer or different: heterotetramer
Type one and type 2 transmembrane protein difference?
1; has N terminus extracellular
2: N terminus intracellular
What are lipid modifications?
covalently attached lipid t help protein bind. Intracellular = acylation and prenylation
Extracellular = GPI anchor
Role of glycosylation?
provides sticky surface, adhesive properties sugar can bind to amino acids
Phosphorylation role?
kinases catalyse, need ATP, gives a negative charge
How is GTP activated and inactivated
by adding and losing a phosphate
What is an SRP used for?
ensuring the protein goes to the correct destination. the receptor is complementary to the signal sequence in the amino acid chain
Steps in protein modification when at ER
- arrives at ER lumen,directed by the signal sequence to the SRP
- once bound SRP released and recycled
- ribosome and protein are at a translator channel and it opens
- protein fed through and signal sequence is cleaved off
What is the role of a chaperone?
ensure the proteins fold correctly as bind to the hydroponic regions that are visible and shouldn’t be and cause hydrolysed to result in change in folding
2 types of chaperone and differenced
Hsp60 - when already folded but wrong, enters a chamber that is then capped and ATP needed
Hsp70 - used when it is actively folding
What if still not folding after chaperone?
targetted and tagged which ubiquitin, causes it to be degraded in proteasome and cleaved into peptides
