Quizzes for Exam 3 MG

How many different DNA Polymerases are involved at the eukaryotic nuclear replication forks?

3

MRNA is read in the __direction, which corresponds to the __of the protein being synthesized.

5' to 3'/N terminus to C terminus

How would one describe the bond that holds the inverted methylguanosine cap on the 5' end of a mature MRNA?

5-5' triphosphate bridge

Why must RNA splicing be absolutely precise?

A single base error at a splice junction within an OFR will change the reading frame and result in MRNA mistranslation.

During translation, chain elongation continues until what happens?

A stop codon is encountered.

Statement A. In eukaryotes the pre-replicative complex (pre-RC) can be formed only during G1 but it remains inactive until the onset of S phase. Statement B. The ability to form pre-RCs or to activate them during ditferent stages of the cell cycle is controlled by the level of activity of Cdk (cyclin dependent kinase) Statement C. ORC in yeast can bind to ARS at any point of the cell cycle.

All statements: A, B and C are true

Which of the following is false about Ames test?

Chemicals that are genotoxic, at concentrations that are not cytotoxic, result in fewer colonies than on the control plates.

Which of the fallowing is false about heat shock or heat shock proteins in E. coli?

Core RNA polymerase is very stable and remains active even above 70 degrees.

All of the following are directly involved in translation except

DNA

The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except

DNA was the first genetic material.

In order to create the replication forks (initiate DNA replication) in E.coli, oriC needs to be "activated". The first step in this process involves binding of ___ proteins to oriC and melting of short stretches of DNA before other proteins can join the complex. During DNA replication ___ protein is required only at oriC.

DnaA

What is the major difference between intron removal of group I and group Il introns?

Group II introns are released as "lariats" but group I introns are released in a linear form.

Which of the following is most likely to interact with a charged bacterial initiator TRNA?

IF-2-GTP

Many of the RNA polymerase Il promoters are TATA-less but they are still recognized by the same specific GTF (general transcription factor) in a sequence specific manner. These promoters must contain___ plus DPE or DCE that are all recognized by a subunit of___

Inr/TAF//TFIID

Which of the following does NOT represent a function of TFIIH?

It has a phosphatase activity necessary for transcript modification

What must the mismatch repair system be able to distinguish in order to tell which nucleotide of a mismatched pair to replace?

It must be able to distinguish the newly-made strand from the parental strand.

A scientist studying fly development isolates two proteins encoded by the same gene that differ from each other by the length of the C-terminal domain. The protein isolated from the head region is identical to the one from the thorax in the N- terminal region but is shorter by 30 amino acids. Analysis of gene sequence indicates a presence of a single ORF that would lead to the production of the longer peptide, the one produced in the thorax. What is the most likely mechanism responsible for the production of the two different peptides encoded by this gene? Hint: draw a picture.

MRNAS in the head region are edited by CDAR generating a premature stop codon.

There are several repair systems in organisms to fix UV radiation "mutations". Which is the only mechanism utilized by humans?

NER

___is the correct designation of consensus sequence for the following sequences: AATGCA GGTGTA TAGGCG CGTATA

NRTGYA

The enzyme peptidyl transferase, which catalyzes the transfer of the polypeptide chain attached to the TRNA in the __site to the aminoacyl-TRNA in the __site, is a(an)__

P; A; FRNA of the large ribosomal subunit

Which of the following are not transcribed from DNA? Select all that apply (if more than 1).

Poly A tails G-caps

Which of the following statements best describes the "termination" of transcription in eukaryotes by RNA Pol II?

RNA polymerase transcribes through the polyadenylation associate with the transcript and cut it free from the polymerase, which continues to signal, causing proteins to synthesize more "nonfunctional" RNA

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript.

Alternative sigma factors are used as a means to regulate gene expression in bacteria. A replacement of one sigma factor for another on bacterial core RNA polymerase will enable

RNA polymerases to initiate transcription using a new (different) set of promoters

Which of the following is/are true?

RNAP III promoters usually contain positions that lie downstream of the startpoint

Many of the RNAP II promoters contain __, an element generally present at a "fixed" distance upstream from startpoint. When present, this element is bound by __via its subunit called__

TATA box/TFIID/TBP

One of the RNA polymerase I ancillary factors, SL1, consists of four proteins. One of its component proteins is also required for the initiation by RNA polymerase Il and RNA polymerase III as a part of a "positioning" factor. This protein common to all three "positioning" factors is called

TBP

In transcription-coupled repair (TCR), how is the presence of a lesion thought to be detected?

The lesion is signaled by a stalled RNA polymerase.

As a ribosome translocates along an MRNA molecule by one codon, which of the following occurs?

The tRNA that was in the A site moves into the P site.

Which of the following is true of snRNPs (snurps)?

They are made up of both protein(s) and snRNA.

Which of the following statements about mammalian telomeres is incorrect?

They can be extended by an enzyme called telomerase that carries an DNA molecule that is complementary to the telomeric repeats.

The codon/codons (all written in 5' to 3') that the molecule in the fig. could interact with is/are (select ALL that apply)

UUA UUG

06- methylG may be ___ generated by and this modified base has a tendency to pair with T. Therefore, if it is not repaired prior to replication its presence in DNA would lead to ___

alkylation/transitions

The RBS or S-D sequence is a consensus sequence found upstream of the start site in MRNAS transcribed from what type of genes? (select all correct answers)

bacterial phage

An eukaryotic cell having a high level of telomerase activity would

be able to proliferate.

Which of the following could have an effect on initiation of DNA replication in E.coli? Select ALL that apply

binding of seqA at oriC the methylation state at oriC binding of DnaA-ATP to oriC

Statement A. The activation of origins of replication is very similar in all organisms and requires sequence-specific binding of initiator proteins, melting of AT rich region by initiators that is followed by recruitment of replication machinery. Statement B. At all origins of replication helicases are loaded, by helicase loaders, directly onto single stranded DNA generated by the initiators.

both A. and B. are false

Which of the following events can occur co-transcriptionally in eukaryotes? (select all correct answers)

capping splicing

In bacteria (E.coli) termination codons are recognized byclass I release factors (RF1 or RF2)

class I release factors (RF1 or RF2)

Water can be DNA's "enemy" by participating in all of the following reactions except:

deamination of Ts converting them to Cs

Many eukaryotic DNA sequences may code for more than one protein in the following way(s) except:

different proteins may be encoded by the same MRNA by utilizing alternative stop codons

Internal Ribosome Entry Sites (IRES) may be present in the mRNAS of to allow for translation of transcripts lacking G-cap. (select all correct answers)

eukaryotes eukaryotic viruses

The function of eukaryotic telomerase is to

extend the lagging strand template at the end of each chromosome

A gene with 13 exons __introns

has 12

A specific eukaryotic transcription unit that is 5,000 nucleotides long uses only 1,200 nucleotides to make a protein consisting of 400 amino acids. This is best explained by the fact that - (select all correct answers).

it may contain several introns that are spliced out. many nucleotides may be present within 5' and 3'UTRS

Assuming there are 9 TCGA sequences within a 600 bp long regulatory region of an eukaryotic gene. How many of these tetramers would you expect to find in a 600 bp sequence anywhere else in the genome assuming that all 4 bases are present in equal proportions.

maybe 2

Which one of the following is not directly involved in mismatch repair in E.coli?

methyltransferase

Concerning the promoters recognized by general sigma factor in E. coli, mutations in the -10 region tend to affect the formation of the complexes and the mutations in the -35 region affect the formation of the __ complexes.

open/closed

Termination (termination and ribosome recycling) of translation involves all of the following except

peptide bond formation

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-GGC 3' (MRNA). The following activated transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. TRNA Anticodon Amino Acid GGC Proline CGU Alanine UGC Threonine CCG Glycine ACG Cysteine CGG Alanine The dipeptide that will form will be

proline-glycine

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to TRNAS with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that

proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Which of the following is not an activity of bacterial core RNA polymerase or any of the eukaryotic RNAPS (I, Il and III)?

recognition of promoters

Which of the following is false about the E. coli general sigma factor (a70)?

removal of C-terminus allows sigma (alone) to bind promoters

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight because their cells have an impaired ability to

remove pyrimidine dimers by NER pathway

Which of the following is not a type of cis-acting element?

repressor

The best term to describe the extension of the lagging strand template at vertebrate telomeres is

reverse transcription.

In the figure below the ESES are (select ALL that apply)

sites within RNA cis-acting elements sites within exons

There are 61 MRNA codons that specify an amino acid, but only at most 45 different TRNAS in a cell. This is best explained by the fact that

some tRNAS have anticodons that recognize two or more different codons.

Which of the following strategies is not used by phages to organize the expression of their genes into regulatory cascades?

successive alternative ribosomes

Which of the following is false about bacterial RNA polymerase catalyzed reactions (synthesis of RNA)?

these reactions occur at the catalytic site located in the sigma subunit

Which of the following is false about nuclear genes for large rRNAs in higher eukaryotes?

they are translated into r-proteins