Molecular biology semester 1 Flashcards
Devires, Correns and Tschermak repeated Medels work. Together they confirmed what?
- the difference between phenotype and genotype.
- Factors which influence traits are passed on through generations.
- Heredity determinants stay the same between generations.
- Some form of material carries this information.
Derives, Correns and Tschermak knew that there was a material that carried genetic information. What did they know that this material must be able to do?
- Must be able to be stored.
- Must be also be replicated.
- Must be able to allow variance.
- Must be able to express itself.
Miescher discovered what from hospital bandages covered in puss?
Nuclein.
Why did Miescher knwo that the substance he found on bandages was not protein?
It contained no sulphur.
What 2 things did Walther Flemming discover via his work on salamander cells?
Chromatin and mitosis.
What did Boverti discover from looking at ascaris embryos?
Meiosis.
What did Sutton discover from looking at grasshoppers?
That different combinations of chromosomes lead to different stereotypes.
Who came up with the theory of inheritance?
Sutton and Boverti.
What does the theory of inheritance consist off?
That chromosomes were needed for embryonic development and ‘factors’ lay among these chromosomes. It coincides with Mendels second law.
What did Thomas Hunt Morgan discover regarding phenotypes?
He discovered the recessive phenotype in Drosphilla leading to a whit eyed mutant.
Apart from discovering the recessive phenotype, what else did Thomas Hunt Morgan discover?
That genes lie on chromosomes. He was also the first to use linkage maps.
What disorder did Garrod study in his work?
Alkaptonuria- a disorder where the patient has black urine and painful joints.
Who proposed for the first time that disease acting in a Mendelian way?
Archibald Garrod.
Archibald Garrod disovered that disease acted in a Mendelian fashion. What else did he discover in regards to genes and metabolism?
He discovered that genes were linked to specific defects and that you can have inborn errors in metabolism.
Who came up with the ‘One gene one enzyme’ hypothesis?
George Beadle and Edward Tatum.
What was the main question answered in the ‘One gene one enzyme hypothesis?’
‘Is there a link between genes and the enzymes responsible in the metabolic processes of Neurospora casa?
What pathway was looked at in the ‘One gene one enzyme’ hypothesis?
The production of niacin from tryptophan.
What can auxotrophic mutants not grow on?
Minimal growth medium.
When was the auxotophic mutant able to grow?
When Niacin and 3-hydroxyanthranilic acid where added to the medium.
What step did the mutant prohibit in the ‘One gene one enzyme’ hypothesis?
The synthesis of 3-hydroxyanthranilic acid from kynureine.
What was crossed to prove the ‘One gene one enzyme hypothesis?’
WT and mutant. There was a one to one segregation proving Mendelian inheritance.
What did the transforming principle show?
That DNA was the genetic material.
Who originally came up with the transforming principle?
Fredrick Griffith.
Why is the S strain of Strepoccus pneumoniae virulent while the R strain is not?
The s strain is smooth as it contains a polysaccharides coat. This protects it from the hosts immune system. the R strain is rough and does not have this coat.
When the mouse was treated with heat killed S and live R did the mouse survive and why?
The mouse did not survive. Some form of material had allowed R to transform into the S strain and kill the mouse.
It was originally not known what caused the transforming principle. Polysaccharides, lipids, RNA and DNA were also suggested. Why did people think it was not DNA?
They thought that DNA was too simple.
Who finally solved the transforming principle by proving that DNA was in fact the genetic material which had passed from the R stain to the S strain?
Oswald Avery, Collin Macleod, Macyln Mccarthy.
How was it shown that DNA was what allowed the transforming principle to happen?
Different components of the S strain were destroyed in turn and the mouse was the inoculated with the modified strain. When RNA, Lipids and Polysaccharides were destroyed the mouse died. When DNA was destroyed the mouse lived. This proved that DNA was the heredity material.
If repeated would the R strain always become virulent when added to a heat killed S strain?
No. It only becomes virulent if it takes up the genes needed for the coat. It is now known that the virulent DNA taken up would have replaced its non virulent counterparts.
What did Hershey and Chase confirm?
That DNA was the genetic material.
What bacteriophage did Hershey and Chase work with?
T2 phage. This can attach to the host with tail fibes.
What two radioactive elements did Hershey and Chase use to label the protein and the DNA?
S35 and P32.
What was present in the supernatent and what was present in the pellet when the T2 phage and the Ecoli were centrifuged?
The phage ghost was present in the suprnatent and the bacterium was present in the pellet.
The Tobacco Mosaic Virus causes lessions on leaves. It was used by Fraenkel- Conrat and Singer to show what?
That some viruses contain RNA instead of DNA.
The protein and RNA were separated in the labs and combinations of the subunits were painted onto leaves. When did the leaves become infected?
When the RNA was painted onto the leaves and when the reconstructed virus was painted onto leaves. It was also infected when the normal TMV was painted on.
A hybrid virus of TMV and _____was used in the second experiment by Conrat and Singer.
HRV - Holmes Ribgrass Virus.
Was the coat of TMV or HRV used in the hybrid virus?
TMV.
What happened when the leaf was infected by the HRV without the presence of the TMV coat and what did this show?
The leaf was infected and the HRV recovered has a HRV coat. This proved that RNA could direct the production of protein subunits.
Are purines or pyramides bigger?
Purines.
Who discovered thymine?
Kossel. He also discovered that purines are bigger than pyramides.
Levene did not believe that DNA was the genetic material as he thought that it was to simple. What did he discover that turned out to be correct?
He identified the sugars found in nucleotides.
Who determined that the ratio of purines and pyamides is the same?
Chargaff.
All organisms have the same amount of A=T. true or false ?
False. Some are more AT rich then others.
Wilkinson and Franklin discovered that DNA has a regular helix pattern with a turn of 3.5nm. How did they do this?
X ray crystallography.
Which base pair is stronger and why?
G=C as it forms three bonds. A=T only forms two.
What bond is formed in the major and minor groove?
Glycosidic bond.
The center of a DNA molecule is ________.
Hydrophillic.
Why does DNA have grooves?
Because the bonds that join the sugar phosphate backbone are not perfectly opposite to each other.
How often is there a helical turn in DNA?
Every 10.5bp.
Who determined the type of replication used?
Meelson and Stanls.
What three models of replication did Meelson and Stanls test?
Conservative, semi conservative and dispersed.
In Meelson and Stanls test did they grow the DNA in heavy or light nitrogenfirst?
Heavy.
What where the DNA strands centrifuged with in Meelson and Stanls experiment?
Caesium chloride. Heavier strands settled at the bottom and light at the top.
How many bands where present in Meelson and Stanls experiment after one generation and what did this mean?
One. This meant it could not be conservative.
After two generations how many bands where present in Meelson and Stanls experiment? What did this mean?
Two bands where present (hybrid and light). This meant that replication had to be semi conservative and not dispersed as dispersed only had one band present.
What happened to the hybrid band in the dispersed model throughput generations?
It got lighter and lighter.
What did John Cairnes do?
Determined the origin of replication in E.coil.
John Cairnes used radioactive labels which he visualised with autoradiography. What did this show DNA replication to be in E.coli?
Bidirectional.
How did John Cairnes confirm semi conservative replication?
There were two labelled strands in the second generation.
How many replication forks are there in E.coli?
2.
How many origins of replication are there in Eukaryotes?
Many.
What did Arthur Kornberg use to study polymerase activity?
A free cell system.
Kornberg separated the proteins in the bacterial cell by electrical charge. By doing this he increased the activity of polymerase by _____ fold.
2000.
What did Kornberg assay the DNA polymerase enriched extract with?
Template DNA, Mg2+ and radiolabelled nucleotides.
What did Kornberg use to locate long pieces of DNA?
Radioactive markers.
In Kornberg’s experiment which strand was radioactive?
The new strand.
What four things did Kornberg confirm with his experiment?
- A free 3’ end is needed for replication
- The DNA needs to be double stranded.
- DNA is made 5’ to 3’
- All four nucleotides are needed along with cofactor Mg2+.
What are the three distinct regions in DNAP1?
- DNA synthesis domain.
- 3’–> 5’ proofreading exonuclease domain.
- 5’–>3’ primer removal exonuclease domain.
What enzyme makes primers?
Primase.
What is the role of tropisomerase in DNA replication?
Binds ahead of the replication fork causing and relives the strain placed on it as it unravels.
What is the role of helicase in DNA replication?
It breaks the hydrogen bonds between the 2 strands allowing the DNA to unwind and from a replication fork.
What is the role of single stranded binding proteins (SSB’S) in DNA replication?
They prevent re annealing of the separate strands by binding to the individual strands and stabilising them.
What is the main polymerase used in DNA replication?
DNAP3.
What is the main polymerase used in DNA repair?
DNAP1.
In addition to DNAP1 and DNAP3 how many other polymerases are there?
3.
There is _______ replication of the leading DNA strand and _______ replication of the lagging strand. ______ _______ are found in the lagging strand. The lagging opposes the fork movement.
Continuous, discontinuous, Okazaki fragments.
What is RNP?
A ribonuceloprotien (RNA bound to protein.)
What two things can stabilise the RNA structure?
- Base pairing.
2. Base stacking interactions.
RNA is folded through intramolecular base paining into what?
Short double stranded stem loops.
What do short RNA helices often form?
Stem loops and hairpins.
________ interactions in RNA define its 3D shape,
Tertiary.
What are the 3 possible tertiary interactions found in RNA?
- Long range base pairing
- Coxial stacking of helices ( resulting in a longer helix.)
- A minor motif.
Is the major groove of RNA deeper and narrower than that of B form DNA or shallower and broader?
Deeper and narrower?
Is the minor groove of RNA deeper and narrower than that of B form DNA or shallower and broader?
Shallower and broader.
What groove do RNA binding proteins usually bind to?
The minor groove.
RNA binding proteins include divalent metal cations. Why do they bind in the minor groove?
They interact with the phosphodiester backbone to equal out the charge of the phosphate.
Some nucleotides are post transcriptionally modified, especially __RNA.
t.
What noncanocial base pair is known as the ‘wobble’ base pair?
G-U.
Is the GU or GA base pair more common?
GA.
Is ‘1,6’ relevant to the purines or the pyramides?
Purines.
2,3,4 is relevant to the pyramides.
Can DNA or RNA contain base triplets?
RNA.
Why is it hard to predict the 3D structure of RNA?
As noncanocial base pairs can form.
What are tetraloops?
Four RNA nucleotides stacked on top of each other.
Loops in RNA are always four nucleotides in size. True or false?
False. They can be larger.
Why are noncanocial base pair interactions important in RNA?
They can alter the dimension if the RNA helix which is important in specific binding interactions. This can including the binding of the second elongation factor.
What percentage of cellular RNA is mRNA?
5%.
What percentage of cellular RNA is rRNA?
75%.
What percentage of cellular RNA is tRNA?
10%.
Apart from mRNA, tRNA and rRNA there are many other small rnas within the cell. What are four examples of these?
- Small nuclear RNA
- Small nucleolar RNA
- micro RNA
- regulatory RNA.
What are all RNAs transcribed as?
Larger precussor molecules with are subsequently processed into mature functional RNAs.
What cleaves specific structures from within the RNA?
endoribonuclease.
Where do exoribonucleases degrade the RNA from?
The free end of the molecule.
What are the proteins called that target polymerase to the promoter regions of specific genes?
Sigma factors.
Does RNAP require additional primers or helicases?
No.
Where are the two promoter regions found in E.coli?
35 and 10 nucleotides upstream.
What do highly conserved/ highly transcribed genes have in regards to their promoter?
A promoter that highly matches the consensus sequence of the 35 and 10(pribnow) boxes.
Is the promoter 35 nucleotides upstream or 10 nucleotides upstream in E.coli called the pribnow box?
10 nucleotides.
Why is the transcription of RNA an essentially irreversible reaction?
As the phosphate produced when a nucleotide is added to the chain is irreversibly hydrolysed.
How many core subunits are there in RNAP found in E.coli and what are they?
alpha, alpha, gamma, beta, beta’.
Where is the DNA binding groove found in RNAP found in E.coli?
Between the beta and beta’ subunits.
What subunits are catalytic in RNAP found in E.coli?
Beta/ beta’.
What subunits bind transcription factors in the RNAP found in E.coli?
Alpha.
What is the purpose of the gamma subunit in the RNAP from E.coli?
It allows assembly and stability.
Apart from increasing the affinity to promotors, what can sigma factors do?
Decrease non specific DNA binding.
What is a holenzyme?
An RNA polymerase bound to a transcription factor.
What sigma factor is used most in E.coli?
70.
What sigma factor is involved in heatshock?
32.
What sigma factor is involved in nitrogen metabolism?
54.
What did this experiment show?
A filter binding assay of protein and radiolabelled DNA was set up. the filter trapped protein which bound to DNA at a varying rate. You can visualise where the DNA is due to its radioactivity. When unlabelled DNA was added it formed a DNA/protein complex on the rate dependant of the breakdown the radioactive DNA/protein complex. The rate of breakdown was much slower when a ______ was used instead of ______.
It showed that sigma factors allow tighter binding of RNAP to DNA.
Haloenzyme
RNAP.
What three things are involved in transcription initiation in prokaryotes?
- Promoter binding
- DNA unwinding
- Primer synthesis.
In prokaryote transcription initiation what happens when the primer reaches 18 nucleotides long?
The alpha subunit of RNAP is released (which binds transcription factors) and the NUSA protein binds.
Why does the NUSA protein bind during transcription initiation in E.coli?
It imparts processivity to the RNAP.
What two things can the NUSA protein prevent in prokaryote transcription?
- Polymerase stalling.
2. Premature transcription termination.
What two methods of transcription termination are present in prokaryotes?
- Intristic termination.
2. rho dependant termination.
There are two methods of transcription termination in prokaryotes. What do they both involve?
Destabilisation of the RNA/DNA heteroduplex with the active site of RNAP. This allows the RNA to dissociate from the RNA/DNA complex.
What structural characteristic of RNA allows for intrinsic termination in prokaryotes?
The stem loop structure with a GC rich stable base region.
What base pairs destabilise the RNA/DNA structure?
ru-da.
Where does the polymerase pause in intrinsic termination in prokaryotes?
The hairpin structure.
What method of transcription termination in prokaryotes is ATP dependant as it involves an ATP dependant helicase?
rho-dependant termination.
What terminator sequence allows rho to bind in termination in prokaryotes?
C rich terminator sequences.
What happens to the polymerase when rho initially binds to the c rich terminator sequence?
It pauses.
Why can rho unwind base pairing between the RNA and DNA?
It has helicase activity.
What has a hexameric ATPase ring structure which can open to allow threading?
rho.
At what step in rho dependant termination is ATP hydrolysed?
When rho meets RNAP.
In what type of organism does compartmentalisation occur?
Eukaryotes.
Compartmentalisation is when transcription and translation occur separately.
How many distinct RNA polymerases are there in eukaryotes?
3.
Which of the eukaryote RNA polymerases contains a CDA tail?
pol2.
What does RNAP1 code for in eukaryotes?
rRNA.
What does RNAP2 code for in eukaryotes?
mRNA.
What does RNAP3 code for in eukaryotes?
5s, tRNA.
How many specific regions does RNAP1 encode for in eukaryotes?
5.
How many specific regions does RNAP2encode for in eukaryotes?
3.
How many specific regions does RNAP3 encode for in eukaryotes?
7.
Mitrochondrial and chloroplast genes are encoded for by RNA polymerase 1. True of False?
False. They have their own polymerases.
What do eukaryotes lack that prokaryotes do not?
Sigma factors.
Eukaryotes do not have sigma factors. What do they use instead?
Transcription factors.
What facilities the assembly of the preinitation complex on the promoter of polymerase 2?
General transcription factors.
What does the preinitiation complex allow?
RNAP2 to bind to the right place.
What is TBP also known as?
The TATA box binding protein?
Where is TBP found?
In TFIID.
The TBP is found in TFIID. What does this bind to in transcription initiation in eukaryotes?
The DNA.
Multiple Transcription factors bind once the TBP in TFIID has bound to the DNA. What are these transcription factors and in what order do they bind in?
TFIIB, TFIIF, TFIIE, TFIIH
The binding of what transcription factors allows RNAP2 to bind to the DNA in transcription initiation in eukaryotes?
TF11F.
Do eukaryotes use intrinsic termination, rho dependant termination or the torpedo model of termination to stop transcription?
The torpedo model.
What is RNAP2 termination coupled to in eukaryotes?
3’ mRNA processing.
In eukaryotes transcription is coupled to 3’ mRNA processing. What carries out this processing?
Cleavage/polyadenylation complex.
What does cleavage by the cleavage/polyadneylation complex allow in transcription termination in eukaryotes?
The downstream fragment to be degraded 5’ to 3’ by the exonuclease Xrn2.
What exonuclease allows very quick degradation the downstream fragment in the torpeado model of termination?
Xrn2.
Allow compartmentalisation is slower what does it allow?
Nuclear processing event. This means that there can be greater diversity in the mRNA’s produced.
What does CTD on RNAP2 contain?
Tandem repeats of serine rich heptapeptide.
How does the CTD tail on RNAP2 change during transcription?
Serine phosphorylation is varied.
How is the CTD tail phosphorylated when capping occurs?
It is phosphorylated at position 5.
How is the CTD tail phosphorylated when polyadneylation occurs?
It is phosphorylated at position 2.
What does the varying pattern of phosphorylation in the CTD tail allow transcription to be coordinated with?
RNA processing.
How does RNAP3 terminate transcription in eukaryotes
With stretches of T’s. This is similar to intristic termination in prokaryotes.
Can slowing down cause RNAP’s to dissociate?
Yes.
Translation can not happen at varying rates. True or False?
False.
Why does capping occur to the 5’ end of mRNA transcripts in eukaryotes?
So the ends are not susceptible to exonucleases.
What process must occur before polyadneylation to expose the 3’ end of the mRNA transcript?
Splicing.
What post transcriptional modification of mRNA happens first?
5’ capping.
What is a ribonucleoprotein complex also known as?
A splicesome.
In eukaryotes do mRNA’s encode a single peptide?
Yes.
Is the poly(A) tail transcribed?
No.
What often ends up degrading the poly(A) tail in eukaryotes?
Xrn2.
The cleavage/polyadenylation complex carries out polyadenylation. What two types of factors does it contain to allow it to do this?
- Cleavage factors.
2. Specificity factors.
RNA processing reactions mainly take place in the cytoplasm. True or false?
False. They mainly take place in the nucleus.
Where is it thought that the splicesome could have evolved from?
Autocatalytic activity of self splicing ribozymes.
A ribozyme is an RNA that can splice itself.
Does the cap structure, poly(A) tail or both prevent degradation?
Both.
Apart from preventing degradation, what is the purpose of the cap and poly(A) tail added to the mRNA after transcription?
They can help to promote translation.
What does the UTR stand for?
Untranslated region. These are found either side of the ORF.
What linkage is found in the mRNA cap structure that is not found anywhere else in nature?
5’-5’ triphosphate linkage.
What is added to all mRNA and pol2 transcripts that is methylated in the n7 position?
A guanosine residue.
The poly(A) tail is the same length in all organisms. True or false?
False, the length varies. In humans it is around 200 and in yeast it is around 700.
When will a mRNA no longer be used?
When the poly(A) tail has become to short. The tail degrades throughout its lifetime.
What cleavage/polyadneylation complex processes the 3’ end of the mRNA. What enzyme actually adds on template adenylates to the transcript?
Poly(A) polymerase.
What is the consensus sequence which allows polyadenylation at the 3’ end?
AAUAAA.
Is Poly(A) polymerase DNA dependant or independent?
Independent. RNAP is an example of a DNA dependant polymerase.
ATP is not required for post translation modification of eukaryotic mRNA. True or False?
False, it is required for polyadneylation.
What did hybridisation of DNA and mature mRNA show?
That some parts of the DNA were removed (exons). This was shown when DNA and mature mRNA were annealed to each other which resulted in there being large loops of DNA not annealed to mRNA.
There is 5 times more exon than intron. True or false?
False. There is 5x more intron.
What are the three highly conserved splicesites in mRNA called?
5’ splicesite, branchpoint and the 3’ splicesite.
Which splicesite is the flowing?
GU
5’ splicesite.
Which splicesite is the flowing?
AC
Branchpoint.
Which splicesite is the flowing?
AG
3’ splicesite.
What assembles the splicesome?
SNURP’s.
What are SNURP’s?
Small nuclear RNPs.
How many distinct ribonucleic particles, involving small nuclear RNA, does a SNURP contain?
5.
Introns are released in the form of a ______.
Lariat.
Dos the splicesome assemble on the pre mRNA intron or exon?
Intron
How many transesterfication reactions does splicing involve?
2.
Does splicing require ATP?
No.
What is the first step of splicing?
2’ hydroxyl group on branchpoint adenosine attacks the 3’ phosphate on the 5’ exon. This forms a 5’-2’ phosphodiester bond which gives rise to a looped lariat. This allows the release of the 5’ exon.
What is the second step of splicing?
The generated 3’ hydroxyl group attacks the 5’ phosphate on the 3’ exon. This releases the lariat and joins the two exons.
What is the significance of Tetrahymena thermophila in transcription?
it contains self splicing RNA.
This was shown in vitro in the absence of protein.
In what way are the introns in Tetrahymena thermophila similar to nuclear pre-RNA?
The intron undergoes two transesterifciation reactions.
Where is it thought that nuclear pre-RNA evolved from?
Self splicing introns, such as those found in Tetrahymena thermophila.
What is the definition of gene expression?
A process in which information from a gene is synthesised into a functional gene product.
Why is gene expression very important? (3 reasons)?
- Avoids chaos
- Less energy wasted/ better use of resources
- Allows response to environmental change.
What type of control is an instant response?
Fine control.
What can fine control do to proteins?
Make them functional/ non functional.
What can fine control do to enzymes?
Turn them on and off.
Fine control can make proteins functional/non functional and can turn enzymes on/off. What can bring about these changes?
Covalently bounded ligands.
What does irreversible fine control involve?
Proteolytic processing.
In reversible fine control ligands can covalently bind to molecules. What else can happen which also brings about a change in gene expression?
Specific amino acids can have functional groups attached or removed.
Phosphorylation, acetylation and ubiquitination, allosterism and feedback inhibition are all examples of what?
Reversible modifications involved in instant responses/ course control.
Acetylation is an example of a reversible instant response involved in fine control. Where does this acyl group come from?
Acetyl coA.
Ubiquitination is an example of a reversible instant response involved in fine control. The donor molecule is ubiquitin. What is the main purpose of ubiquitination?
It tags proteins to be degraded. It is involved in cyclin and cell cycle determination.
What enzyme turns the pyruvate dehydrogenase complex on?
Enzyme PDH phosphatase.
What enzymes turns the pyruvate dehyrodgenase complex off?
Enzyme PDH kinase.
What type of reversible modification involves the pyruvate dehydrogenase complex?
Phosphorylation.
When the pyruvate dehydrogenase complex is bound to a phosphate group is it active or inactive?
Inactive.
What is allosterism?
Reversible ligand binding.
In allosterism an inhibitor can bind to the active site. What other type of molecule is involved in allosterism and can influence enzyme activity?
An enhancer.
What happens in feedback inhibition ( an example of reversible fine control)?
The products of a reaction interact with the enzymes active site to ensure that too much of something isn’t made. It also slows down the overall reaction.
DHAP catalysing the first step of aromatic amino acid biosynthesis is an example of what type of reversible fine control?
Feedback inhibition. The aromatic amino acids can inhibit the pathways.
What type of control are delayed responses also known as?
Course control.
What type of gene expression control results in slower changes that are long term?
Course control.
Is the regulation in the amount of proteins an example of course control or fine control?
Course control.
Course control involves long term negative responses. True or False?
False. it can also involve long term positive responses.
Course control can occur at different levels. What level of control is more important in prokaryotes?
Transcriptional.
What happens at the 5’ end of mRNA in prokaryotes as soon as it becomes available?
A ribosome will attach.
In prokaryotes can multiple ribosomes attach to as single mRNA transcript?
Yes.
If the sequence is exactly the same in multiple sequences/places is it said to be conserved sequence or a consensus sequence?
A conserved sequence. a consensus sequence has a high frequency of similarity.
What do DNA binding proteins do?
Regulate the rate in which RNAP binds to the promoter in prokaryotes.
How do DNA binding proteins bind to the DNA.
Through DNA recognition motifs- the most common of these being the helix turn helix.
What part of the DNA do DNA binding proteins bind to?
Major groove.
What does each helix turn helix motif contain?
A recognition helix.
The amino acid side chains of the recognition helix interact with what?
Exposed base pairs on the DNA.
DNA binding protiens can bind to DNA via common motifs, such as the helix turn helix. These can bind to DNA via the side chains on the recognition helix and exposed base pairs. What happens next?
A second helix lies on top to help position the recognition helix. It can also increase the binding affinity.
Positive control with DNA binding proteins increases the rate of transcription. True or false?
True.
Negative control will decrease the rate of transcription.
How many genes are there approximately in the E.coli genome?
400-600 genes.
Around 4000 proteins can be encoded for by E.coli. How many will be encoded for at a given time?
600-800.
When are constitutively expressed genes expressed?
Always. Their genes and enzymes are always needed.
What is the role of housekeeping genes?
They encode proteins that help with maintenance.
Housekeeping genes are important but are not constitutively expressed. True or false?
False. They tend to be constitutively expressed, at least in a tissue specific manner.
it is assumed that the expression of housekeeping genes is unaffected by what?
Experimental conditions.
The expression of facultative/responsive/adaptive genes depends on what?
Environmental stimuli.
Can inducible genes be switched on or off?
On.
Can repressible genes be switched on or off?
Off. (They are also off when transcription is prevented.)
Gene expression can be looked at from the mRNA level or from the protein level. Which is more important?
Protein level, however looking at the at the mRNA level is easier.
What 6 things can influence the level of protein production?
- The number of genes for that protein in the genome.
- Time spent in transcription/translation.
- Promotor efficiency.
- Promoter strength.
- Variable strength of the ribosomal binding site.
- The half life of the mRNA made.
Why is EFTU expressed often expressed at a different level to other proteins in the E.coil genome?
There are 2 copies of the EFTU gene in the genome. Most genes only have one copy.
What causes variation in promoter strength?
Variation in the promoter sequence.
What sequence varies to distinguish the strength of the ribosomal binding site?
The shine delgaro sequence (this helps recruit rRNA). Ribosomal binding sites that greatly match the shine delgaro sequence will bind with more strength and efficiency to the rRNA that weaker sequences would.
What is this sequence also known as ?
UAAGGAG.
The shine delgaro sequence.
