rna replication Flashcards
codon
base triplet of mRNA . mRNA transport genetic info o protein synthesis.
anti-codon
tRNA transport amino acid to ribosomes for protein synthesis
protein synthesis
translation. coded amino acids are built in the protein chain
DNA replication
Forwarding genetic info into a new cell during cell division.
replication
it is semiconservative , this is ,the produced new double helix is composed of 1 parental and 1 newly synthesised strand.
3 phases of DNA replication
initiation, elongation, termination
initiation in prokaryotes
start point = replication origo , that is composed of consensus sequences
dna A (initiation in prokaryotes )
proteins recognise replication origo and bind to dnaA binding sites
dnaB and dnaC (initiation in prokaryotes)
- bind to DNA A protein
- they have helices activity
- H-bonds between complementary base pairs get split
- double helix opens at replication oligo and replication bubble is formed.
Single Strand Binding Proteins (SSB- proteins) (initiation in prokaryotes)
complementary base pairs are not allowed to match again so as to keep two strands separate from each other.
synthesis of new strand (initiation in prokaryotes)
free 3’-OH-group is needed.
primers bind to parental dna single strands
primer
a short RNA sequence with free 3’-OH-group
synthesis of primers
happens by primosomes
Primosome is a protein complex, where the most important component is primase enzyme, synthesising primer
elongation of replication in prokaryotes
the second step of replication
Leading strand(elongation in prokaryotes)
continuous synthesis happens • Only one primer is needed
Lagging strand (elongation in prokaryotes)
discontinuous synthesis happens , several short fragments are formed.
Okazaki fragment
primer+ Dna
DMA polymerase III (elongation in prokaryotes)
is responsible for the synthesis of the new DNA stranddirection of synthesis is 5’3’
(DNA dependent DNA polymerase III)
building nucleotides in the new strands
Deoxyribonucleoside triphosphate (dNTP) –> Deoxyribonucleoside monophosphate (dNMP) are built in + inorganic pyrophosphate is released
termination of replication in prokaryotes
third phase of replication where -DNA polymerase III dissociates.
- DNA polymerase I hydrolyses and remove primers
DNA polymerase I (termination in prokaryotes)
- hydrolyse and cut out primers (with 5’-3’ exonuclease activity)
- with 5’-3’ polymerase activity , fills space between separate DNA fragments by building appropriate nucleotides in the chain
DNA ligase
ligation of newly synthesised DNA fragments at sugar-phosphate backbone (uses ATP for the formation of phosphodiester bonds)
function of DNA ligase
- DNA ligase hydrolyses one ATP to AMP and PPin so, the activated AMP molecule binds to enzyme
- The 5’-end of DNA fragment forms phosphodiester bond with the 3’-end of the neighboring DNA fragment
- AMP dissociates from the enzyme
topoisomerase
remove tenseness during replication
