RNA Replication Mutation Flashcards
What is Codon?
Base triplets of mRNA
mRNA transports genetic information for protein synthesis
What is Anticodon?
Base triplets of tRNA
(tRNA transports amino acids to ribosomes for protein synthesis)
What is Translation?
= Protein synthesis -> coded amino acids are built in the protein chain
What happens during replication?
DNA double helix splits into two single strands, serving as a Template (pattern) for the formation of the new strand by base pairing
What does it mean that the Replication is semiconservative?
= the produced new double helix is composed of one “parental” (derived from the original cell) and one newly synthesised strand
What are the 3 phases of DNA replication?
- Initiation (1)
- Elongation (2)
- Termination (3)
Initiation of replication in Prokaryotes:
Begins at the Startpoint = Replication Origo (composed of consensus sequences: similar sequences in all living organisms)
Function of dnaA proteins?
They recognice replication origo and bind to dnaA binding sites (in inititation of replication in Prokaryotes)
Function of dnaB and dnaC proteins?
- They bind to dnaA protein
- They have helicase activity
(initiation of replication in prokaryotes)
What does it mean that dnaB and dnaC has helicase activity?
Prokaryotes
H-bonds between complementary base pairs get split -> double helix opens at replication origo and “replication bubble” (also called “replication fork”) is formed.
(inititation of replication in prokaryotes)
What is the function of Single Strand Binding Proteins (SSB-proteins)
(Prokaryotes)
They keep the two strands separate from each other (when complemetary base pairs are not allowed to match again)
(inititaion of replication in prkaryotes)
What is a Primer?
Prokaryotes
A short RNA sequence with free 3´-OH-group
How do synthesis of primers happen?
Prokaryotes
By Primosomes
- Primosome is a protein complex where the most important component is primase enzyme, synthesising primer.
Continous synthesis happens in?
Prokaryotes
Leading strand.
Only one primer is needed
What is Lagging strand?
Prokaryotes
Discontinous synthesis happens, several short fragments are formed.
What is Okazaki-fragment?
Prokaryotes
One primer is needed for each single fragments (in lagging strand)
-> primer + DNA together are called Okazaki-fragment
What is responsible for the synthesis of the new DNA strand?
Prokaryotes
DNA polymerase III (DNA-dependent polymerase III)
- Direction of synthesis is 5´-> 3´
How is the building of nucleotides in the new strands?
Prokaryotes
Deoxyribonukleoside triphosphate (dNTP) -> Deoxyribonukleoside monophosphate (dNMP) are built in + inorganic pyrophosphate is released.
Elongation of replication in Prokaryotes?
DNA polymerase III builds new nucleotides in new strands -> continous synthesis on leading strand, while discontinous synthesis on lagging strand (okazaki-fragments)
At the end of replication (at terminus sequence)?
DNA polymerase III dissociates
DNA polymerase I:
- Primers are hydrolysed and cut out by DNA polymerase I.
- Fills space between separate DNA fragments by building appropriate nucleotides in the chain.
What is DNA ligase?
Ligation of newly synthesised DNA fragments at sugar-phosphate backbone (uses ATP for the formation of phosphodiester bonds)
Termination of replication in Prokaryotes:
- DNA polymerase I. hydrolyses and removes primers, then completes the strand with newly synthesised DNA fragments.
- DNA ligase ligates the backbone of DNA fragments.
Functions of DNA ligase?
- DNA ligase hydrolyses one ATP to AMP and PPin -> the activated AMP molecules binds to enzyme
- The 5´-end of DNA fragments forms phosphodiester bond with the 3´-end of the neighboring DNA fragment
- AMP dissociates from the enzyme
Function of Topoisomerases?
Tenseness and twist of DNA strands during replication
Proteins needed for replication are organised in?
Replisome
DNA polymerase operates as a dimer, which means?
-> replication of two DNA strands happens simultaneously.
Which one of Eukaryotes or Prokaryotes has numerous origos?
Eukaryotes
What does numerous replication mean?
Numerous replisomes -> replication happens at different places at the same time.
DNA polymerase alpha?
Synthesis of new DNA strand
(Eukaryotes)
(equals with DNA plymerase III of Prokaryotes)
DNA polymerase beta?
Repair of DNA during replication
(Eukaryotes)
(Equals with DNA polymerase II of Prokaryotes)
DNA polymerase gamma
?
Replication of mitochindrial DNA
DNA polymerase delta?
Synthesis of new DNa strand (further from primer)
- Needs PCNA (proliferating cell nuclear antigen) protein for operation
What is a Telomere?
Extra sequence attached to the 3´end of chromosome, rich in G-bases
(only eukaryote)
Containes no genetic information, so loss of these sequences during replication causes no problem?
Telomere
What is Telomerase?
Enzymes synthesise telomeric sequences (even more active in gametes and tumor cells -> more cell division is possible than normally)
What is mutation?
Changes in the structure of DNA that result in heritable changes in the coded genetic formation
Mutations results in?
- genetic diseases
- cancer
- evolution
Types of Mutations?
Type 1: - Spontaneous - Induced (UV/radiation/chemicals) Type 2: - gametic - Somatic Type 3: - Chromosme - gene/point
Types of Point mutations?
- Substitution
- Missense (code other amino acid)
- Nonsense (code STOP)
- Silent or samesense (code the same amino acid) - Insertion
- Frame shift mutation - Deletion
- Frame shift mutation
Types of Mutagenesis?
Nitrites, nitrates, oxidative deamination, UV radiation, Timin dimers (covalent bonds between two pyrimidine base), Malignus melanoma, Repair by deletion
