week 5- microbial genetics Flashcards
of chromosomes?
Eukaryotic DNA
shape?
Present in?
telomeres present or no?
introns present or no?
Strands?
sugar?
Linear
Present in nucleus
Telomeres
Introns
Multiple chromosomes
Strands twist
deoxyribose
of chromosomes?
prokaryotic DNA
shape?
Present in?
telomeres present or no?
introns present or no?
Strands?
Sugar?
Circular structure
Present in cytoplasm
No telomeres
No introns
Only one chromosome
Bidirectional replication (single origin)
ribose
DNA supercoiling?
- DNA is helical and will form coils
- Supercoiling loosens up the DNA, making it easier to do. separate the two strands
Amino acid structure?
Protein structure?
- central carbon with a carboxyl group (c-terminus), an amino group (N-terminus), and a side chain
- amino acids linked by peptide bonds btwn c and n
Central dogma?
- DNA makes RNA through transcription, and RNA makes polypeptides through translation
what is the replication fork? Replicon? Direction of DNA?
- is where DNA is unwound
- Replicon- portion of the genome that contains an origin and is replicated as a unit
- bidirectional replication from a single origin (circular bacterial. DNA)
helicase
disrupts H-bonds and helps move the replisome
SS DNA binding protein
protects DNA from damage
Topoisomerase
relives twisting of unwound DNA
primase
synthesizes short RNA primers (~10bp) for DNA polymerase
clamp loader complex
holds DNA polymerase at the DNA strand
Tau
binds and organizes R coli replication proteins
leading strand?
Leading - once opened, DNA polymerase adds complementary strands 5 to 3
What does the polymerase require? How many DNA pol does E. col have?
- template, primer and dNTPs
- 5 with pol 3 playing major role in replication
lagging? process?
- lagging strand, prompted by primers and synthesizes short Okazaki fragments
- DnaA protein binds origin, causing bending and separation of strands
- helicase separates strands, SSB binds
- primase synthesizes RNA primer
- lagging and leading made
- DNA pol 1 removes RNA primers and fills in gaps with DNA
- Okazaki fragments are joined by DNA ligase
How does proofreading happen?
- carried out by DNA pol 3, removes mismatch bases from the 3’ end of the growing strand by the exonuclease activity of the enzyme
- not 100% effective
how does termination in E. Coli happen?
- stops when replisome reaches termination site on DNA, catanes form when topoisomerase breaks and rejoins DNA strands to ease supercoiling and recombinase enzyme catalyzes intramolecular crossover that separates the two strands
What is the bacterial RNA polymerase made of?
- core enzyme = 5 polypeptides
- sigma factor - helps core enzyme recognize the start of the genes
- RNA pol haloenzyme= core enzyme + sigma factor (only haloenzyme can begin transcription)
What does RNA pol use in euk and prokaryotes to initiate transcription?
- TATA box
- prib now box
What is the process of initiation of transcription in bacteria? What are the two bacterial promoters?
- sigma factor helps position core enzyme at the promoter
- 35 bps upstream - sigma factor recognizes
- 10bps upstream - where DNA strands start to separate
how does rna pol initate trabscription ?
- the promoter contains a region where the sigma factor recognizes (-35 bps upstream) and a Pribnow box (-10 downstream) where DNA strands start to separate and transcription starts are (+1)
- (-) upstream and before transcription
Where does the repressor protein bind? activator/
- repressor = operator region
- enhancer region
what is the process of transcription elongation?
- after binding, RNA pol unwinds DNA and processes 5 to 3
- forms a transcription bubble - moves with pol as it synthesizes mRNA and w/in bubble a temporary RNA:DNA hybrid formed
- dNTPs incorporated into RNA, complementary to DNA template
Transcription termination process?
Two mechanisms?
- when core RNA pol dissociates from template DNA
- DNA sequences mark the end of the gene and terminator
- intrinsic termination - common - stem-loop formation (
- factor-dependent - rho protein (helicase)