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RNA polymerase question

RNA polymerase question


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In this question we are examining a bacterial RNA polymerase that elongates at 20 codons per second. Question 1: How long will this RNA polymerase take to transcribe the Lac Z gene at 3510 base pairs?

My answer: A codon is 3 base pairs so I start by dividing 3510 by 3 and then by 20 to get 58,5 seconds.

Question 2: Your bacteria can produce a Lac Z mRNA about every other second. How can you explain this?

My answer: I am very lost on this one. I thought that the mRNA would be as long as the gene so wouldn't this be 58,5 seconds not roughly 2 seconds??


Multiple RNA Polymerase transcription complexes engaged on the lacZ gene at the same time, staggered along the gene.


Either the gene is present in multiple copies (especially possible if it is in a plasmid) or multiple RNA polymerases are transcribing it, each beginning from the start site one after the other with some amount of time delay, much like multiple ribosomes translate the same mRNA to increase rate of protein production.


Question 1.
In a DNA strand the nucleotides are linked together by
(a) glycosidic bonds
(b) phosphodiester bonds
(c) peptide bonds
(d) hydorgen bonds.
Answer:
(b) phosphodiester bonds

Question 2.
The net electric charge on DNA and histones is
(a) both positive
(b) both negative
(c) negative and positive, respectively
(d) zero.
Answer:
(c) negative and positive, respectively

Question 3.
Which of the following statements is the most appropriate for sickle cell anaemia ?
(a) It cannot be treated with iron supplements.
(b) It is a molecular disease.
(c) It conferes resistance to acquiring malaria.
(d) All of the above.
Answer:
(d) All of the above.

Question 4.
The first genetic material could be
(a) protein
(b) cabohydrates
(c) DNA
(d) RNA.
Answer:
(d) RNA.

Question 5.
The human chromosome with the highest and least number of genes in them are respectively
(a) chromosome 21 and Y
(b) chromosome 1 and X
(c) chromosome 1 and Y
(d) chromosome X and Y.
Answer:
(c) chromosome 1 and Y

Question 6.
Who amongst the following scientist had no contribution in the development of the double helix model for the structure of DN A ?
(a) Rosalind Franklin
(b) Maurice Wilkins
(c) Erwin Chargaff
(d) Meselson and Stahl
Answer:
(b) Maurice Wilkins

Question 7.
Which of the following steps in transcription is catalysed by RNA polymerase ?
(a) Initiation
(b) Elongation
(c) Termination
(d) All of the above
Answer:
(d) All of the above

Question 8.
Control of gene expression takes place at the level of
(a) DNA-replication
(b) transcription
(c) translation
(d) none of the above.
Answer:
(b) transcription

Question 9.
Which was the last human chromosome to be completely sequenced ?
(a) Chromosome 1
(b) Chromosome 11
(c) Chromosome 21
(d) Chromosome X
Answer:
(a) Chromosome 1

Question 10.
In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called
(a) A – DNA
(b) B – DNA
(c) cDNA
(d) rDNA.
Answer:
(c) cDNA

Question 11.
If the sequence of initrogen bases of the coding strand of DNA in a transcription unit is: 5’ – ATGAATG – 3’, the sequence of bases in its RNA transcript would be
(a) 5’ – AUG A AUG – 3’
(b) 5’ – UACUU AC – 3’
(c) 5’ – CAUUCAU – 3’
(d) 5’ – GUAAGUA – 3’.
Answer:
(d) 5’ – GUAAGUA – 3’.

Question 12.
The RNA polymerase holocnzyme transcribes
(a) the promoter, structural gene and the terminator region.
(b) the promoter and the terminator region
(c) the structural gene and the terminator region
(d) the structural gene only.
Answer:
(b) the promoter and the terminator region

Question 13.
If the base sequence of a codon in mRNA is 5’ – AUG – 3′ the sequence of tRNA pairing with it must be
(a) 5’ – UAC – 3’
(b) 5’ – CAU – 3’
(c) 5’-AUG – 3’
(d) 5’ – GUA – 3’
Answer:
(b) 5’ – CAU – 3’

Question 14.
The amino acid attaches to the tRNA at its
(a) 5’- end
(b) 3’ – end
(c) anticodon site
(d) DHUloop.
Answer:
(b) 3’ – end

Question 15.
To initiate translation, the wiRNA first bind to
(a) the smaller ribosomal sub-unit
(b) the larger ribosomal sub-unit
(c) the whole ribosome
(d) no such specificity exists.
Answer:
(a) the smaller ribosomal sub-unit

Question 16.
In E. colt, the lac operon gets switched on when
(a) lactose is present and it binds to the repressor
(b) repressor binds to operator
(c) RNA polymerase binds to the operator
(d) lactose is present and it binds to RNA polymerase.
Answer:
(a) lactose is present and it binds to the repressor

Question 17.
In DNA strand, the nucleotides are linked together by
(a) glycosidic bonds
(b) phosphodiester bonds
(c) peptide bonds
(d) hydrogen bonds.
Answer:
(b) phosphodiester bonds

Question 18.
If a double stranded DNA has 20% of cytosine, what will be the percentage of adenine in it ?
(a) 20%
(b) 40%
(c) 30%
(d) 60%
Answer:
(c) 30%

Question 19.
If the sequence of bases in one strand of DNA is ATGCATGCA, what would be the sequence of bases on complementary strand ?
(a) ATGCATGCA
(b) AUGCAUGCA
(c) TACTACGT
(d) UACGUACGU
Answer:
(c) TACTACGT

Question 20.
How far is each base pair from the next one in DNA double helix model ?
(a) 2 nm
(b) 3.4 nm
(c) 34 nm
(d) 0.34 nm
Answer:
(d) 0.34 nm

Question 21.
Synthesis of DNA from RNA is explained by
(a) central dogma reverse
(b) reverse transcription
(c) feminism
(d) all of these.
Answer:
(d) all of these.

Question 22.
Histone proteins are
(a) basic, negatively charged
(b) basic, positively charged
(c) acidic, positively charged
(d) acidic, negatively charged
Answer:
(b) basic, positively charged

Question 23.
The structure in chromatin seen as ‘beads-on string’ when viewed under electron microscope are called
(a) nucleotides
(b) nucleosides
(c) histone octamer
(d) nucleosomes.
Answer:
(d) nucleosomes.

Question 24.
Find out the wrong statement about heterochromatin,
(a) It is densely packed
(b) It stains dark.
(c) It is transcriptionally active.
(d) It is late replicating.
Answer:
(c) It is transcriptionally active.

Question 25.
They year 2003 was celebrated as the 50th anniversary of discovery of
(a) transposons by Barbare Me Clintock
(b) structure of DNA by Watson and Crick
(c) Mendel’s laws of inheritance
(d) biotechnology by Kary Muliis.
Answer:
(b) structure of DNA by Watson and Crick

Question 26.
The process of transofrmation is not affected by which of the following enzymes ?
A. DNase
B. RNase
C. Peptidase
D. Lipase
(a) A, B
(b) A, B, C, D
(c) B, C, D
(d) A, B, C
Answer:
(c) B, C, D

Question 27.
The three codons which result in the termination of polypeptide chain synthesis are
(a) UAA, UAG, GUA
(b) UAA, UAG, UGA
(c) UAA, UGA, UUA
(d) UGU,UAG,UGA
Answer:
(b) UAA, UAG, UGA

Question 28.
Amino acids which are specified by single codons are
(a) phenylalanine and arginine
(b) tryptophan and methionine
(c) valine and proline
(d) methionine and aroinine.
Answer:
(b) tryptophan and methionine

Question 29.
Which out of the following statements is incorrect ?
(a) Genetic code is ambiguous.
(b) Genetic code is deqenerate.
(c) Genetic code is universal.
(d) Genetic code is non-overlanning.
Answer:
(a) Genetic code is ambiguous.

Question 30.
Some amino acids are coded by more than one codon, hence the genetic code is
(a) overlapping
(b) degenerate
(c) wobbled
(d) unambiguous.
Answer:
(d) unambiguous.

Question 31.
The mutations that involve addition, deletion or substitution of a single pair in a gene are referred to as
(a) point mutations
(b) lethal mutations
(c) silent mutations
(d) retrogressive mutations.
Answer:
(a) point mutations

Question 32.
Sickle cell anemia results from a single base substitution in a gene, thus it is an example of
(a) point mutation
(b) frame-shift muttion
(c) silent mutation
(d) both (a) and (b).
Answer:
(a) point mutation

Question 33.
Select the incorreclty matched pair.
(a) Initation codons – AUG,GUG
(b) Stop codons – UAA, UAG, UGA
(c) Methionine – AUG
(d) Anticodons – mRNA
Answer:
(d) Anticodons – mRNA

Question 34.
Amino acid acceptor end of tRNA lies at
(a) 5’ end
(b) 3’ end
(c) T VC loop
(d) DHUloop.
Answer:
(b) 3’ end

Question 35.
Which RNA carries the amino acids from the amino acid pool to mRnA during protein synthesis ?
(a) rRNA
(b) mRNA
(c) /RNA
(d) hnRNA
Answer:
(c) /RNA

Question 36.
During translation, activated amino acids get linked to tRNA. This process is commonly called as
(a) charging of tRNA
(b) discharging of tRNA
(c) aminoacylation of tRNA
(d) both (a) and (c)
Answer:
(b) discharging of/RNA

Question 37.
To prove that DNA is the genetic material, which radioactive isotopes were used by Hershey and Chase (1952) in experiments ?
(a) 33S and 15N
(b) 32P and 35S
(c) 32P and 15N
(d) 14N and 15N
Answer:
(d) 14N and 15N

Question 38.
RNA is the genetic material in
(a) prokaryotes
(b) eukaryotes
(c) Tabacco Mosaic Virus (TMV)
(d) E.coli.
Answer:
(c) Tabacco Mosaic Virus (TMV)

Question 39.
Which one among the following was the first genetic material ?
(a) DNA
(b) RNA
(c) Protein
(d) Nuclein
Answer:
(b) RNA

Question 40.
Which of the following life processes is evolved around RNA ?
(a) Metabolism
(b) Translation
(c) Splicing
(d) All of these
Answer:
(b) Translation

Question 41.
Chemically, RNA is (i) reactive and (ii) stable as compared to DNA.
(a) (i) equally, (ii) equally
(b) (i) less, (ii) more
(c) (i) more, (ii) less
(d) (i) more, (ii) equally
Answer:
(c) (i) more, (ii) less

Question 42.
Which of the following phenomena was experimentally proved by Meselson and Stahl ?
(a) Transformation
(b) Transduction
(c) Semi-conservative DNA replication
(d) Central dogma
Answer:
(c) Semi-conservative DNA replication

Question 43.
First experimental proof for semi-conservative DNA replication was shown in
(a) Streptococcus pneumoniae
(b) Escherichia coli
(c) Neurospora crassa
(d) Rattus rattus.
Answer:
(b) Escherichia coli

Question 44.
Select the correct match of enzyme with its related function.
(a) DNA polymerase – Synthesis of DNA strands
(b) Helicase – Unwinding of DNA helix
(c) Ligase – Joins together short DNA segments
(d) All of these
Answer:
(d) All of these

Question 45.
Other than DNA polymerase, which are the enzymes involved in DNA synthesis ?
(a) Topoisomerase
(b) Helicase
(c) RNA primase
(d) All of these
Answer:
(d) All of these

Question 46.
DNA replication takes place at _________ phase of the cell
cyle.
(a) G1
(b) S
(c) G2
(d) M
Answer:
(b) S

Question 47.
The process of copying genetic information from one strand of DNA to RNA is termed as _________ .
(a) replication
(b) transcription
(c) translation
(d) reverse transcription
Answer:
(b) transcription

Question 48.
The enzyme DNA dependent RNA polymerase catalyses the polymerisation reaction in ___________direction.
(a) only 5’ → 3’
(b) only 3’ → 5’
(c) both (a) and (b)
(d) none of these
Answer:
(a) only 5’ → 3’

Question 49.
If the sequence of bases in coding strand of DNA is ATTCGATG, then the sequence of bases in mRNA will be
(a) TAAGCTAC
(b) UAAGCUAC
(c) ATTCGATG
(d) AUUCGAUG.
Answer:
(d) AUUCGAUG.

Question 50.
If the sequence of bases in DNA is GCTTAGGCAA then the sequence of bases in its transcript will be
(a) GCTTAGGCAA
(b) CGAATCCGTT
(c) CGAAUCCGUU
(d) AACGGAUUCG.
Answer:
(c) CGAAUCCGUU

Question 51.
Transcription unit
(a) starts with TATA box
(b) starts with pallendrous regions and ends with rho factor.
(c) starts with promoter region and ends in terminator region
(d) starts with CAAT region.
Answer:
(c) starts with promoter region and ends in terminator region

Question 52.
During transcription, the site of DNA molecule at which RNA polymerase binds is called
(a) promoter
(b) regulator
(c) receptor
(d) enhancer.
Answer:
(a) promoter

Question 53.
Polycistronic messenger RNA (mRNA) usually occurs in
(a) bacteria
(b) prokaryotes
(c) eukaryotes
(d) both (a) and (b)
Answer:
(d) both (a) and (b)

Question 54.
In transcription in eukaryotes, heterogenous nuclear RNA (hnRNA) is tmascribed by
(a) RNA polymerase I
(b) RNA polymerase II
(c) RNA poly merase II
(d) all of these.
Answer:
(b) RNA polymerase II

Question 55.
Methyl guanosine triphosphate is added to the 5’ end of hnRNA in a process of
(a) splicing
(b) capping
(c) tailing
(d) none of these
Answer:
(b) capping

Question 56.
In eukaryotes, the process of processing of primary transcript involves
(a) removal of introns
(b) capping at 5’end
(c) tailing (polyadenlation) at 3’ end
(d) all of these.
Answer:
(b) capping at 5’end

Question 57.
In a n/RNA molecule, untranslated regions (UTRs) are present at
(a) 5’ – end (before start codon)
(b) 3’ – end (after stop codon)
(c) both (a) and (b)
(d) 3’- end only.
Answer:
(c) both (a) and (b)

Question 58.
UTRs are the untranslated regions present on
(a) rRNA
(b) hnRNA
(c) mRNA
(d) hnRNA.
Answer:
(c) mRNA

Question 59.
Which of the following statements is correct regarding ribosomes ?
(a) Most of a cell’s DNA molecule are stored there.
(b) Complete polypeptide is released from there.
(c) mRNAs are produced there.
(d) DNA replication takes place there.
Answer:
(b) Complete polypeptide is released from there.

Question 60.
Regulation of gene expression occurs at the level of
(a) transcription
(b) processing/splicing
(c) translation
(d) all of these.
Answer:
(d) all of these.

Question 61.
During expression of an operon, RNA polymerase binds to
(a) structural gene
(b) regulator gene
(c) operator
(d) promoter.
Answer:
(d) promoter.

Question 62.
The sequence of structural genes in lac operon is
(a) Lac A, Lac Y, Lac Z
(b) Lac A, Lac Z, Lac Y
(c) Lac Y, Lac A, Lac A
(d) Lac Z, Lac Y, Lac A
Answer:
(d) Lac Z, Lac Y, Lac A

Question 63.
Which of the following cannot act as inducer ?
(a) Glucose
(b) Lactose
(c) Galactos
(d) Both (a) and (c)
Answer:
(d) Both (a) and (c)

Question 64.
Human genome consists of approximately
(a) 3 × 10 9 bp
(b) 6 × 10 9 bp
(c) 20,000 – 25,000 bp
(d) 2.2 × 10 4 bp.
Answer:
(a) 3 × 10 9 bp

Question 65.
Estimated number of genes in human beings is
(a) 3,000
(b) 80,000
(c) 20,500
(d) 3 × 10 9
Target Series Objective Guide Science (English Medium)
Answer:
(c) 20,500

We hope the given Biology MCQs for Class 12 with Answers Chapter 6 Molecular Basis of Inheritance will help you. If you have any query regarding CBSE Class 12 Biology Molecular Basis of Inheritance MCQs Pdf, drop a comment below and we will get back to you at the earliest.


Structural Biology of RNA Polymerase II Transcription: 20 Years On

Gene transcription by RNA polymerase II (Pol II) is the first step in the expression of the eukaryotic genome and a focal point for cellular regulation during development, differentiation, and responses to the environment. Two decades after the determination of the structure of Pol II, the mechanisms of transcription have been elucidated with studies of Pol II complexes with nucleic acids and associated proteins. Here we provide an overview of the nearly 200 available Pol II complex structures and summarize how these structures have elucidated promoter-dependent transcription initiation, promoter-proximal pausing and release of Pol II into active elongation, and the mechanisms that Pol II uses to navigate obstacles such as nucleosomes and DNA lesions. We predict that future studies will focus on how Pol II transcription is interconnected with chromatin transitions, RNA processing, and DNA repair.

Keywords: RNA polymerase X-ray crystallography cryo-electron microscopy gene transcription structural biology transcriptional regulation.


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  1. In prokaryotes the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted unicode[Arial] , unicode[Arial] , unicode[Arial] , and unicode[Arial] ’, comprise the polymerase core enzyme. The fifth subunit, unicode[Arial] , is involved only in transcription initiation. The polymerase comprised of all five subunits is called the holoenzyme.
  2. In prokaryotes the polymerase is composed of four polypeptide subunits, two of which are identical. These subunits, denoted unicode[Arial] , unicode[Arial] , unicode[Arial] , and unicode[Arial] ’, comprise the polymerase core enzyme. There is a fifth subunit that is involved in translation initiation. The polymerase comprised of all four subunits is called the holoenzyme.
  3. In prokaryotes the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted unicode[Arial] , unicode[Arial] , unicode[Arial] , and unicode[Arial] ’, comprise the polymerase holoenzyme. The fifth subunit, unicode[Arial] , is involved only in transcription initiation. The polymerase comprised of all five subunits is called the core enzyme.
  4. In prokaryotes the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted unicode[Arial] , unicode[Arial] α, unicode[Arial] , and unicode[Arial] ’, comprise the polymerase core enzyme. The fifth subunit, unicode[Arial] , is involved only in termination. The polymerase comprised of all five subunits is called the holoenzyme.
  1. Rho-dependent termination is controlled by rho protein and the polymerase stalls near the end of the gene at a run of G nucleotides on the DNA template. In rho-independent termination, when the polymerase encounters a region rich in C-G nucleotides the mRNA folds into a hairpin loop that causes the polymerase to stall.
  2. Rho-independent termination is controlled by rho protein and the polymerase stalls near the end of the gene at a run of G nucleotides on the DNA template. In rho-dependent termination, when the polymerase encounters a region rich in C-G nucleotides, the mRNA folds into a hairpin loop that causes polymerase to stall.
  3. Rho-dependent termination is controlled by rho protein and the polymerase begins near the end of the gene at a run of G nucleotides on the DNA template. In rho-independent termination, when the polymerase encounters a region rich in C-G nucleotides, the mRNA creates a hairpin loop that causes polymerase to stall.
  4. Rho-dependent termination is controlled by rho protein and the polymerase stalls near the end of the gene at a run of G nucleotides on the DNA template. In rho-independent termination, when the polymerase encounters a region rich in A-T nucleotides, the mRNA creates a hairpin loop that causes polymerase to stall.
  1. Rho-independent termination involves the formation of a hairpin.
  2. Rho-dependent termination involves the formation of a hairpin.
  3. Rho-dependent termination stalls when the polymerase begins to transcribe a region rich in A-T nucleotides.
  4. Rho-independent termination stalls when the polymerase begins to transcribe a region rich in G nucleotides.
  1. The initiation step in eukaryotes requires an initiation complex with enhancers and transcription factors. Also, the separation of the DNA strand is different as histones are involved.
  2. The initiation step in prokaryotes requires an initiation complex with enhancers and transcription factors. Also, the separation of the DNA strand is different as histones are involved.
  3. The elongation step in eukaryotes requires an initiation complex with enhancers and transcription factors. Also, the separation of the DNA strand is different as histones are involved.
  4. The initiation step in eukaryotes requires an initiation complex with enhancers and transcription factors. Also, the separation of the DNA strand is different as histones are not involved.
  1. No, because they have the same unicode[Arial] -amanitin sensitivity in all products.
  2. No, quantitative analysis of products is done to determine the type of polymerase.
  3. Yes, they can be determined as they differ in unicode[Arial] -amanitin sensitivity.
  4. Yes, they can be determined by the number of molecules that bind to DNA.
  1. No, alternative splicing can lead to the synthesis of several proteins from a single gene.
  2. Yes, alternative splicing can lead to the synthesis of several forms of mRNA from a single gene, building more complex proteins.
  3. No, alternative splicing can lead to the synthesis of several forms of codons from a set of genes.
  4. Yes, alternative splicing can lead to the synthesis of several forms of ribosomes from a set of genes, but only one protein per gene.
  1. exporting the mRNA across the nuclear membrane
  2. importing the mRNA across the nuclear membrane
  3. the mRNA staying inside the nuclear membrane
  4. the mRNA translating into proteins within seconds
  1. The transcript would degrade when the mRNA moves out of the nucleus to the cytoplasm.
  2. The mRNA molecule would stabilize and start the process of translation within the nucleus of the cell.
  3. The mRNA molecule would move out of the nucleus and create more copies of the mRNA molecule.
  4. The mRNA molecule would not be able to add the poly-A tail on its strand at the 5’ end.
  1. The mRNA would be 5’-AUGGCCGGUUAUUAAGCA-3’ and the protein will be MAGY.
  2. The mRNA would be 3’-AUGGCCGGUUAUUAAGCA-5’ and the protein will be MAGY.
  3. The mRNA would be 5’-ATGGCCGGTTATTAAGCA-3’ and the protein will be MAGY.
  4. The mRNA would be 5’-AUGGCCGGUUAUUAAGCA-3’ and the protein will be MACY.
  1. rRNA has catalytic properties in the large subunit and it assembles proteins.
  2. rRNA is a protein molecule that helps in the synthesis of other proteins.
  3. rRNA is essential for the transcription process.
  4. rRNA plays a major role in post-translational processes.
  1. The anticodon will match the codon in mRNA.
  2. The anticodon will match with the modified amino acid it carries.
  3. The anticodon will lose the specificity for the tRNA molecule.
  4. The enzyme amino acyl tRNA synthetase would lose control over the amino acid.

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    Examiners report

    Most candidates gained some marks here with knowledge of functions of proteins with examples. However many answers were very descriptive rather than &ldquostating with an example&rdquo as asked.

    Most knew about the two ribosome subunits and the mRNA binding site. Very few knew that they were made from protein and rRNA. Several answered that there were 3 binding sites, but not what was bound there (tRNA) or what they were called.

    The process of transcription was well known by most candidates who attempted this question.


    Silly question, fidelity of RNA polymerase - transcription is 100% error free ? (Oct/28/2006 )

    we all know DNA polymerase do make some error in PCR, but,
    how about RNA polymerase ? I haven't heard about that.

    I don't think this enzyme can be totally error free, right ?
    and that means protein being overexpressed (or normally expressed in organism) would contain some "mutant" ?

    may be 1 million molecule contain only one "mutant" and cannot be detected. however, would that be a problem in molecule screening, for example, ribosome-display screening?

    RNA polymerase makes errors too.
    But effects are relatively minimized by the fact a non sense RNA may be degraded faster and the fact the true half life of an mRNA is very short.
    If you consider the RNAs that have longer half life, like pol III ones, the copy number of them is so great that you have plenty fully functional ones and that drive the uncorrect one negligible.

    The commercially available reverse transcriptases produced by Promega are quoted by their manuals as having error rates in the range of 1 in 17,000 bases for AMV and 1 in 30,000 bases for M-MLV.

    well, I don't know is that too silly to ask this question

    we all know DNA polymerase do make some error in PCR, but,
    how about RNA polymerase ? I haven't heard about that.

    I don't think this enzyme can be totally error free, right ?
    and that means protein being overexpressed (or normally expressed in organism) would contain some "mutant" ?

    may be 1 million molecule contain only one "mutant" and cannot be detected. however, would that be a problem in molecule screening, for example, ribosome-display screening?

    RNA polymerase is not the same as reverse transcriptase. RNA polymerase is not used in PCR, to my knowledge. RNA polymerase has a fidelity about 10 fold worse than DNA polymerase (wild type E coli RNA pol compared to any of the wild type E coli DNA pols.)

    I don't know the fidelity of reverse transcriptase. Given the life cycle and life style of a retrovirus, I would assume that revese transcroptase has a lower fidelity (more errrors) than DNA pol.

    Of course, the commercially available DNA pol Taq's have varying degrees of fidelity.

    If you mean RT enzyme's, they have higher error rates than DNA polymerases, (taq, pfu, any other). Recently, stratagene has released a new one with lower error rate: http://www.stratagene.com/products/display. ct.aspx?pid=700.
    Don't know if it's any good.
    If you consider RT-PCR, you indeed have the possibility of inserting an error during cDNA synthesis, but during the PCR itself you have 35 cycles during which you can "create errors".
    So, if you RT-PCR for sequencing, consider the fact that on a population level, you won't see too much RT or PCR errors, but on a clonal basis you will have errors, brought in during PCR or RT steps.

    (btw: retroviruses depend on their error prone reverse transcription for survival, estimates of their error rates vary from about 1/5000 or so to 1/30000).

    Actually, I am talking about RNA polymerase not reverse transcriptases
    I know they are different, former is from DNA to RNA and the latter is from RNA to DNA

    I just wonder, in normal protein expression, is there any error occur ? and the protein obtained is not the thing I want indeed.

    There should be errors occur in normal protein expression, but abnormal protein amounts to very very little compare to normal protein, and can be ignored (or you could not detect it). I think

    and do remember abnormal/misfolded proteins are targeted for degradation.

    And in eukaryotes, there is a RNA monitoring system, that degrades mRNA which have premature stop codons within the transcript.

    Actually, I am talking about RNA polymerase not reverse transcriptases
    I know they are different, former is from DNA to RNA and the latter is from RNA to DNA

    I just wonder, in normal protein expression, is there any error occur ? and the protein obtained is not the thing I want indeed.

    Yes, there is a lot of error in a wild type scenario there is about 10 fold more error in transcription than in replication.

    I believe this is because DNA pol has a very good proofreading function.

    Higher errors are tolerated in transcription because a few bad transcripts out of thousands of good ones, will not kill off a cell. In replication, a mistake can be fatal to the daughter cell.

    But why did you mention PCR, in this case? RNA pol has very little to do with PCR. Are you thinking about the mRNA that you might harvest for use as a template in RTPCR?

    -Patty, an old transcription person

    Actually, I am talking about RNA polymerase not reverse transcriptases
    I know they are different, former is from DNA to RNA and the latter is from RNA to DNA

    I just wonder, in normal protein expression, is there any error occur ? and the protein obtained is not the thing I want indeed.

    Yes, there is a lot of error in a wild type scenario there is about 10 fold more error in transcription than in replication.

    I believe this is because DNA pol has a very good proofreading function.

    Higher errors are tolerated in transcription because a few bad transcripts out of thousands of good ones, will not kill off a cell. In replication, a mistake can be fatal to the daughter cell.

    But why did you mention PCR, in this case? RNA pol has very little to do with PCR. Are you thinking about the mRNA that you might harvest for use as a template in RTPCR?

    -Patty, an old transcription person

    Thank,
    and why I mention PCR is because, they are both polymerase

    I just afraid of it ---- Recombinant protein which is used for medical use and should be injected into blood. Then, if those protein being expressed by bacteria contain significant amount of toxic protein, say, 0.1%, it should be a problem.

    One of a lecture in our department is doing a project like this, therefore, I want to know the error rate of RNA polymerase in bacteria.


    What is RNA Polymerase 3

    RNA polymerase 3 is the type of eukaryotic RNA polymerase that mainly transcribes tRNA genes. It also transcribes 5S rRNA genes and U6 spliceosomal RNA genes. The genes that are transcribed by RNA polymerase 3 are housekeeping genes whose function is essential for a living cell. Hence, the expression of RNA polymerase 3 is tightly-regulated during cell growth. The transcription of tRNA genes and 5S rRNA genes are initiated by separate transcription factors.

    Figure 3: tRNA Structure


    RNA Polymerase and TATA Box question

    I was looking over this link, and I just wanted to clarify that the RNA polymerase binds to the TATA box? Or does it bind infront/near it?

    The TATA-binding protein binds to the TATA box. Then a couple of transcription factors (TFIID, TFIIA, TFIIB) bind to that area. Then, RNApolymerase binds to that protein complex and gets shit rolling

    I thought it binds on the TATA Box? Don't enhancers/repressors binds near/upstream the RNA polymerase binding site?

    Would you say it binds near the TATA box, and the TBP is what actually binds the TATA box?

    Yeah the TATA binding protein (TBP) is what binds to the actual TATA box. Then the other transcription factors are recruited. Then RNA polymerase binds to the complex of transcription factors that are formed.

    Also look at the image I linked

    Sorry u/runthisfade I meant to have this be a reply to your comment but I'm on mobile


    NEET Biology Molecular basis of Inheritance / विरासत का आणविक आधार Question Bank

    Identify the correct labelling of A, B, C, D & E. Given diagram represents the schematic structure of a transcription unit with some parts labeled as A B C and D. Select the option which shows its correct labeling. Which of the following is/are correct matching(s)?
    Codon Amino acid
    (i) [^<5'>AU<^<3'>>] Serine
    (ii) [^<5'>AU<^<3'>>] Tyrosine
    (iii) [^<5'>AU<^<3'>>] Methionine
    (iv) [^<5'>GU<^<3'>>] Valine
    Select the two correct statements out of the four (i - iv) given below about lac operon.
    (i) Glucose or galactose may bind with the repressor and inactivate it.
    (ii) In the absence of lactose the repressor binds with the operator region.
    (iii) The z-gene codes for permease.
    (iv) This was elucidated by Francois Jacob and Jacque Monod.
    Match column-I with column-II and select the correct answer using the codes given below.
    Column-I Column-II
    A. Operator site I. Binding site for RNA polymerase
    B. Promoter site II. Binding site for repressor molecule
    C. Structural gene III. Codes for enzyme protein
    D. Regulator gene IV. Codes for repressor molecules
    Identify the statements pertaining to the regulatory genes (R), associated with the lac operon that are incorrect.
    (i) mRNA is transcribed from the R gene whether lactose is present or not.
    (ii) mRNA is transcribed from the R gene only when the lactose is present.
    (iii) mRNA is transcribed from the R gene only when the lactose is not present.
    (iv) Lactose inhibits the translation or R gene mRNA.
    The given figure shows lac operon model and its functioning. Select the option which correctly labels A, B, X, Y and Z marked in the figure and also identify the label (L) which is primarily responsible for the hydrolysis of the disaccharide, lactose, into galactose & glucose.
    A B X Y Z L
    Repressor Inducer [eta ]-Galactosidase Permease Transacetylase X
    done clear Identify the labels A, B, C and D in the given structure of t RNA and select the correct option.


    Watch the video: RNA polymerase Question. #MolecularBiology (October 2022).