Transcription and Regulation

Q1: Transcription by E. coli polymerase occurs in

A four phases known as initiation, propagation, elongation and termination

B three phases known as initiation, elongation and termination

C two phases known as initiation and termination

D none of the above

ANS:B - three phases known as initiation, elongation and termination

Please explain the answer.

Q2: RNA is synthesized on a DNA template in a process called __________ , which utilizes the enzyme __________

A translation, RNA polymerase

B transcription, DNA polymerase

C transcription, RNA polymerase

D replication, DNA polymerase

ANS:C - transcription, RNA polymerase

No answer description is available.

Q3: Which of the following conditions would cause the release of the lac repressor protein from the lac operator site on DNA?

A Presence of glucose in the growth media

B Presence of lactose in the growth media

C Presence of IPTG (isopropyl thiogalactoside) in the growth media

D Both (b) and (c)

ANS:D - Both (b) and (c)

What is the effect on the lac operon when cAMP levels are lower and vice versa? Please explain me.

Q4: The transcriptional regulatory proteins in eukaryotes which induce transcription usually have

A at least two distinct domains of protein structure, a DNA binding domain and an activation domain

B at least two distinct domains of protein structure and a DNA binding domain

C at least one distinct domains of protein structure, a DNA binding domain and an activation domain

D none of these

ANS:A - at least two distinct domains of protein structure, a DNA binding domain and an activation domain

Can anyone tell me why it is A and not C? I got a bit confused after looking at all textbooks.

Thanks!

Q5: Upstream regions which are essential for correct transcription are called

A enhancers

B start codons

C promoters

D transcription factors

ANS:C - promoters

No answer description is available.

Q6: Transcription results in

A an amino acid chain

B messenger RNA

C complementary DNA

D Okazaki fragments

ANS:B - messenger RNA

Transcription is a process in which m-RNA is synthesized from DNA.

Q7: The closed complex at bacterial promoters is

A in equilibrium with free RNA polymerase and the promoter

B not affected by promoter mutations

C bound more tightly when repressors are present

D not affected by activator proteins

ANS:A - in equilibrium with free RNA polymerase and the promoter

No answer description is available.

Q8: Which of the following is necessary for transcription to occur?

A DNA molecule

B RNA polymerase

C DNA polymerase

D Both DNA & RNA polymerase

ANS:D - Both DNA & RNA polymerase

One strand of DNA acts as template strand having promoter region required for sigma factor (of RNA polymerase) to identify initiation site.

Q9: The RNA polymerases that transcribe bacterial DNA are

A multisubunit enzymes

B only active inside the cell

C interchangable with DNA polymerases

D highly glycosylated in their active forms

ANS:A - multisubunit enzymes

No answer description is available.

Q10: Most transcripts of protein coding genes are cleaved

A at the 3' end just after a poly adenylation signal

B at the 3' end just before a poly adenylation signal

C at the 5' end immediately after a poly adenylation signal

D at the 5' end immediately before a poly adenylation signal

ANS:A - at the 3' end just after a poly adenylation signal

No answer description is available.

Q11: Each tRNA molecule has a cloverleaf secondary structure consisting of

A three stem loops

B two stem loops

C four stem loops

D either (a) or (b)

ANS:A - three stem loops

No answer description is available.

Q12: Multiple copies of 5S genes, located at a chromosomal site distinct from the other rRNA genes

A are transcribed by rRNA polymerase III and the 5S rRNA

B are transcribed by rRNA polymerase II

C are transcribed by rRNA polymerase I and the 5S rRNA

D are transcribed by DNA polymerase I

ANS:A - are transcribed by rRNA polymerase III and the 5S rRNA

Explain the answer.

Q13: Transcription begins

A at the start codon

B upstream from the start codon

C downstream from the start codon

D none of these

ANS:B - upstream from the start codon

No answer description is available.

Q14: The major function of RNA polymerase's sigma factor is

A recognition of the translational stop sequence

B recognition of the transcriptional start sequence

C recognition of the transcriptional stop sequence

D recognition of the translational start sequence

ANS:B - recognition of the transcriptional start sequence

Sigma factor protein is a sub unit of RNA polymerase.

It's role is to recognize the promoter sequence on a DNA (gene) and binding of RNA polymerase to promoter region.

Q15: RNA polymerase in prokaryotes has a removable

A alpha subunit

B beta subunit

C both (a) and (b)

D sigma subunit

ANS:D - sigma subunit

Sigma subunit is a factor that attaches to rna-polymerase. Rna-polymerase cannot recognise promoter on DNA strand so sigma factor binds to rna-polymerase in order to attach properly to promoter region and cover all consensus sequence.

Q16: In prokaryotes, transcription is

A terminated by the stop codon

B terminated by a protein called rho

C terminated by a poly A sequence

D terminated by a start codon

ANS:B - terminated by a protein called rho

Option B is correct.

In prokaryotes, termination occurs by two ways:

a. Intrinsic mechanism- here, RNA polymerase is destabilized hence, the chain is terminated.
b. Rho-dependent mechanism- Rho protein, basically, a helicase unwinds DNA-RNA hybrid, thus chain is terminated.

Q17: The complex of RNA polymerase, DNA template and new RNA transcript is called

A transcription bubble

B replication bubble

C a translation bubble

D none of these

ANS:A - transcription bubble

Transcription mean that synthesis of RNA from DNA so that RNA polymerase used in transcription process then initiation of transcription so formed this process transcription bubble.

Q18: The regions of a gene located at -10 and -35, with respect to the start of transcription, are termed

A start codons.

B oriC regions.

C Shine Dalgarno sequences.

D promoters.

ANS:D - promoters.

No answer description is available.

Q19: Promoters for tRNAs are located

A upstream from the start codon

B downstream from the start codon

C both (a) and (b)

D none of these

ANS:B - downstream from the start codon

Upstream for prokaryotes And rarely downstream for RNA pol 3 of eukaryotes.

Q20: What is a promoter?

A A specific sequence of DNA to which a catabolic repressor binds

B A specific sequence of DNA to which RNA polymerase binds

C A specific DNA sequence to which a restriction endonuclease binds

D None of the above

ANS:B - A specific sequence of DNA to which RNA polymerase binds

Promotor are specific region division two part upstream and downstream region and present -10 sequence (TATA box region) and -35 sequence. This is part of promote and bind RNA polymerase then start transcription.

Q21: The nucleons of eukaryotic cell has

A RNA polymerase I

B RNA polymerase II

C RNA polymerase III

D all of these

ANS:D - all of these

No answer description is available.

Q22: Enhancers are regions that

A bind RNA polymerase

B are adjacent to the TATA box

C are CAT box binding proteins

D modulate transcription

ANS:D - modulate transcription

No answer description is available.

Q23: Transcription of each set of rRNA genes by RNA polymerasel produces

A a single 45S rRNA precursor molecule

B a single 5S rRNA precursor molecule

C a single 18S rRNA precursor molecule

D a single 28S rRNA precursor molecule

ANS:A - a single 45S rRNA precursor molecule

No answer description is available.

Q24: In both eukaryotes and prokaryotes, a promoter region that is rich in AT bases is called as

A CATT

B Shine Dalgarno region

C TATA box

D SV40 region

ANS:C - TATA box

It is called tata box in eukaryotes only not in prokaryotes, it is called Pribnow bow in prokaryotes.

Q25: Immediately after transcription

A a methylated guanine cap is added to the 51 end of the transcript

B a methylated guanine cap is added to the 31 end of the transcript

C both (a) and (b)

D a poly adenylation signal is added

ANS:A - a methylated guanine cap is added to the 51 end of the transcript

Methylated guanine cap is added to the 51 is not after the transcription, it is added during the transcription.

Q26: The binding of lac repressor to DNA could be considered to be analogous to

A competitive inhibition of an enzyme

B mixed-type inhibition of an enzyme

C uncompetitive inhibition of an enzyme

D allosteric effects in enzyme regulation

ANS:A - competitive inhibition of an enzyme

No answer description is available.

Q27: In eukaryotes, there are three different RNA polymerases. The RNA polymerase responsible for transcription of mRNA is

A RNA polymerase I

B RNA polymerase II

C RNA polymerase III

D none of these

ANS:B - RNA polymerase II

No answer description is available.

Q28: RNA polymerase holoenzyme initiates transcription which involves

A recognition of the -10 sequence and -35 sequence

B recognition of the -10 sequence only

C recognition of the -35 sequence only

D none of the above

ANS:A - recognition of the -10 sequence and -35 sequence

Both are consensus sequences.

-10 sequence (TATAAT) is also called the Pribnow box.

Q29: Rho-dependent termination of transcription in E. coli

A requires ATP

B requires about 50 nucleotides of uncomplexed mRNA

C both (a) and (b)

D removes mRNA and holoenzyme from the DNA

ANS:C - both (a) and (b)

How the answer C is correct?

Q30: The function of the sigma factor of RNA polymerase is to

A assure that transcription begins at the proper point

B assure that transcription ends at the proper point

C assure that translation begins at the proper point

D assure that translation ends at the proper point

ANS:A - assure that transcription begins at the proper point

Sigma is subunite of rna polymeras, which recognize the promoter and help in transcription initiation.

Q31: Transcription factors are

A promoters

B proteins which bind to DNA and regulate transcription

C TATA boxes

D CATT boxes

ANS:B - proteins which bind to DNA and regulate transcription

No answer description is available.



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