DNA replication and gene expression Flashcards
What does DNA rep require?
Template and primer
What is the direction of DNA ?
5’ >3’
What are Purines?
Adenine and Guanine
What are Pyrimidines?
Thymine and Cytosine
What is prokaryotic DNA?
circular
What is phosphodiester bond?
between phosphate and 3’0H of next nucleotide
How many H bonds between Guanine and Cytosine?
3 H bonds
What is semi conservative rep.?
Template strand is original parent
What happens in semi conservative rep?
original parent unwinds> 2 template strands
What enzyme used on Replication fork?
DNA polymerase
What is used to unwind DNA ?
DNA binding proteins
Enzymes -HELICASES
Hydrolysis of ATP
How many origins of replication in prokaryotes ?
1 since circular DNA
What primes DNA replication?
RNA Primer - Primase synthesises it
What is Exonucleases?
For proof reading and remove wrong nucleotide
- catalyses synthesis of dNTPs
What happens at replication fork in SCR?
Leading strand synthesised continuously
Lagging strand synthesised in Okazaki Fragments
What joins okazaki fragments ?
DNA Ligase
What adds new nucleotides to primers in SCR?
DNA POLYMERASE 3 - synthesises both lagging and leading strand
What replaces the primer with DNA ?
DNA POLYMERASE 1
What is the primosome?
primase and helicase
What does Helicase do?
unwind the chain and break H bonds
What stabilizes DNA?
Single strand binding proteins
What does transcription make ?
RNA
What are transcription steps?
1) Initiation
2) elongation
3) Termination
What happens during Initiation ?
RNA polymerase binds to PROMOTER sequence
where are promoter region found?
Upstream of start site like TATA Box
What does RNA polymerase do?
unwinds base pairs of template DNA in transcription bubble
What is TATA box called in prokaryotes?
Pribnow box
What happens during Elongation?
RNA polymerase proceeds along DNA template srand
What is produced in elongation??
RNA product that is identical to non template strand but RNA has Uracing and not Thymine in DNA
How does transcription terminate?
RHO INDEPENDANT
RHO DEPENDANT
What is Rho independent termination ?
when mRNA HAIRPIN formed and causes RNA polymerase to stall
How is mRNA liberated in rho independent ?
weak mRNA interactions with template DNA
What is Rho Dependant termination?
Termination is RHO protein based
What happens in Rho dependant?
helicase rho binds to RNA and pulls away from RNA polymerase and DNA template so mRNA released
What is RHO protein?
Helicase
What strands are identical?
mRNA and coding strand but U not Thymine for mRNA
What does transcription not require ?
PRIMERS
