Exam 3 genetics

DNA Polymerase I from E. coli was the first DNA polymerase to be purified. This enzyme has a unique enzymatic activity that has not been found with any other DNA polymerase in E. coli. That unique activity is __________ (hint: it is used to remove the RNA primers during DNA replication). 3' to 5' exonuclease 5' to 3' polymerase Reverse transcriptase 5' to 3' exonuclease 3' to 5' polymerase

5' to 3' exonuclease

The following diagram represents DNA that is part of the RNA-coding sequence of a transcription unit. The bottom strand is the template strand. What is the sequence of the RNA that results from transcription of this DNA? 5'-A T A G G C G A T G C C A-3' 3'-T A T C C G C T A C G G T-5' 5'-A U A G G C G A U G C C A-3' 5'-U A U C C G C U A C G G U-3' 5'-A T A G G C G A T G C C A-3' 5'-A C C G U A G C G G A U A-3' 5'-U G G C A U C G C C U A U-3'

5'-A U A G G C G A U G C C A-3'

Introns are characterized by which of the following invariant consensus sequences? 5' GU-intron-UG 3' 5' CG-intron-CG 3' 5' GU-intron-UA 3' 5' GU-intron-AG 3' 5' UU-intron-GG 3'

5'GU-intron-AG 3'

Which of the following mutations would probably cause constitutive (continuous) expression of a bacterial operon? Mutations in An enhancer sequence that prevented binding of the appropriate transcriptional activator. A repressor protein (such as the lac repressor) that was unable to bind to the operator region. The deletion of the -10 box (TATA Box) consensus sequence in the promoter. An enhancer sequence that moved it 200 bp upstream from its unusual position. Select this answer if none of the choices A-D are correct.

A repressor protein (such as the lac repressor) that was unable to bind to the operator region.

Isoforms (also called variants) are different polypeptides that are produced from the same pre-mRNA in eukaryotic cells. These polypeptides are usually the result of Transcription by RNA Polymerase I instead of RNA Polymerase II. Alternative splicing of the pre-mRNA by telomerase. Alternative splicing of the exons of the pre-mRNA. Alternative tRNA anticodons that recognize different codons and, thus, change the amino acid sequence of the polypeptide. None of the above because isoforms are only made in prokaryotic cells.

Alternative splicing of the exons of the pre-mRNA.

Which of the following statements is NOT correct about the process of transcription? A. Transcription of a given gene takes place on only one of the two DNA strands. B. During transcription the RNA molecule is synthesized in the 3' to 5' direction. C. During transcription the RNA molecule that is synthesized is anti-parallel and complementary to the template DNA strand. D. The start site and direction of transcription are determined by a region of the nontemplate DNA strand known as the promoter.

B. During transcription the RNA molecule is synthesized in the 3' to 5' direction.

In eukaryotes, which RNA polymerase transcribes the genes that encode proteins? A. RNA polymerase I B. RNA polymerase II C. RNA polymerase III D. RNA polymerase IV E. RNA polymerase V

B. RNA polymerase II

In E. coli, the primer used for DNA synthesis is A. a free DNA nucleotide B. a short stretch of RNA nucleotides. C. a 3' OH group that is part of the primase enzyme. D. None of the above are correct because DNA synthesis does not require a primer.

B. a short stretch of RNA nucleotides.

Eukaryotic cells typically have 75-200 copies of the genes encoding ribosomal RNAs. These genes would be classified as ____________. A. highly repetitive DNA B. moderately repetitive DNA C. unique-sequence DNA

B. moderately repetitive DNA

Okazaki fragments are associated with synthesis of: A. the leading strand B. the lagging strand C. both the leading and the lagging strands D. single-stranded circular DNA

B. the lagging strand

Does this picture depict polyribosomes in prokaryotic or eukaryotic cells? A.EUKARYOTIC B.PROKARYOTIC C.CANNOT BE DETERMINED

B.PROKARYOTIC

For a(n) __________ operon, transcription normally does NOT take place, and it is kept off by a(n) _________. A.inducible; activator B.inducible; repressor C.repressible; activator D.repressible; repressor

B.inducible; repressor

Some organisms that are morphologically and physiologically less complex than humans actually have larger genomes. This phenomenon is known as the Transformation effect C-value paradox Hypochromic effect Excessive replication conundrum Dosage compensation paradox

C-value paradox

DNA replication in eukaryotes differs from replication in prokaryotes in that: A. DNA replication in eukaryotes is conservative, whereas in prokaryotes it is semiconservative. B. Eukaryotes have bidirectional replication from an origin, whereas in prokaryotes replication proceeds in one direction from an origin. C. Eukaryotic chromosomes have many separate origins of replication, whereas prokaryotic chromosomes have a single origin of replication. D. Linear eukaryotic chromosomes are replicated by a mechanism called theta replication, whereas circular prokaryotic chromosomes are replicated by the rolling circle mechanism.

C. Eukaryotic chromosomes have many separate origins of replication, whereas prokaryotic chromosomes have a single origin of replication.

Which of the following is NOT a correct description of how translation differs between bacteria and eukaryotic cells? A. In bacterial cells transcription and translation can occur simultaneously, whereas in eukaryotic cells these processes occur in different cellular locations. B. In prokaryotes, the small ribosomal subunit associates with the mRNA at the Shine-Dalgarno sequence, whereas in eukaryotes the small ribosomal subunit first associates with the 5'cap of the mRNA. C. In prokaryotes the initiator codon is recognized by met-tRNA, whereas in eukaryotes the initiator codon is recognized by fmet-tRNA.

C. In prokaryotes the initiator codon is recognized by met-tRNA, whereas in eukaryotes the initiator codon is recognized by fmet-tRNA.

A single gene can yield multiple types of mRNA by all of the following mechanisms EXCEPT: A. alternative splicing of the exons of the pre-mRNA B. use of alternative 3' cleavage and polyadenylation sites in the pre-mRNA. C. shuffling the order of the exons in the mRNA relative to their order in the DNA. D. Examples of all of the above have been found.

C. shuffling the order of the exons in the mRNA relative to their order in the DNA.

DNA polymerases are considered processive because A. they bind to a substrate, carry out one catalytic event, disengage and reinitiate synthesis on another DNA molecule. B. they create a pool of nucleotides that covalently bind to their corresponding complimentary bases. C. the same polymerase molecule catalyzes multiple cycles of nucleotide additions to a polynucleotide chain. D. they bidirectionally synthesize DNA as long continuous chains. E.none of these

C. the same polymerase molecule catalyzes multiple cycles of nucleotide additions to a polynucleotide chain.

Any given mRNA sequence has ______ possible reading frames, and the correct one is determined by a(n)___________________. A.2; termination codon B.4; initiation codon C.3; initiation codon D.3; termination codon E.2; initiation codon

C.3; initiation codon

You have isolated what appears to be alien DNA. While studying its replication, you performed the exact experiment Meselson and Stahl did. After three generations, the DNA is subjected to a CsCl gradient, and only one band appears. What type of replication does this DNA undergo?A.Semiconservative B.Conservative C.Dispersive D.Replication of the alien DNA may be either semiconservative or conservative. The experimental results cannot distinguish between the two possibilities. E.The experimental results do not support any of the three possible mechanisms of replication.

C.Dispersive

In eukaryotic cells, nearly all of the unique DNA that encodes proteins is found in A.Heterochromatin B.Homochromatin C.Euchromatin D.Prochromatin E.None of the above is correct because eukaryotic cells do not have repetitive DNA.

C.Euchromatin

Which of the following would most likely contain genes with the greatest number of introns? A.E. coli cells B.Yeast cells C.Human cells D.Mitochondria E.Bacteriophage lambda

C.Human cells

What would the likely result be if a specific sigma subunit were mutated? A.Nothing would result: sigma is not essential. B.RNA polymerase would still bind at specific sites, but elongation would fail. C.RNA polymerase would fail to initiate transcription at the promoter specific to the sigma subunit. D.The core enzyme would not be stable.

C.RNA polymerase would fail to initiate transcription at the promoter specific to the sigma subunit.

An in vitro transcription system that contains a bacterial gene does not initiate transcription. What is one possible problem? A.Histones that were on the DNA when it was isolated from E. coli are blocking access to the template. B.There is a mutation in the inverted repeat sequence that prevents a hairpin secondary structure from forming. C.There is a mutation at -10, where a promoter consensus sequence is located. D.Rho factor has not been added.E.TATA-binding protein (TBP) has not been added.

C.There is a mutation at -10, where a promoter consensus sequence is located.

Which statement is true regarding the binding of an amino acid to a tRNA? A.Amino acids bind to the 5' end of the tRNA. B.The binding of amino acids to tRNAs requires GTP. C.There is one aminoacyl tRNA synthetase for each of the 20 amino acids. D.Each aminoacyl tRNA synthetase recognizes a different tRNA.

C.There is one aminoacyl tRNA synthetase for each of the 20 amino acids.

During initiation of DNA replication in E. coli, what is the role of helicase? A. It binds to the origin and causes a short section of the double helix to unwind. B. it binds to and stabilizes the single-stranded DNA. C. it reduces torsional strain by controlling supercoiling ahead of the replication fork. D. it continues the unwinding of the dsDNA at the replication fork that was started by the initiator proteins. E. it synthesizes the RNA primers for the Okazaki fragments.

D. it continues the unwinding of the dsDNA at the replication fork that was started by the initiator proteins.

A(n) __________ operon is normally turned on, and it is turned off by a(n) _________._________. A. inducible; activator B. inducible; repressor C. repressible; activator D. repressible; repressor

D. repressible; repressor

Which of the following is considered a secondary structure of proteins? A.Hairpin loops B.Helix-turn-helix domains C.Stem-loops D.Alpha helix E.Zinc fingers

D.Alpha helix

The TATA-binding protein (TBP) binds to the TATA box sequence in eukaryotic promoters. What is its function in transcriptional initiation? A.It blocks access of RNA polymerase to the promoter, until removed by general transcription factors. B.It is the subunit of prokaryotic RNA polymerase that is required to recognize promoters. C.It modifies histones so that nucleosomes can be removed from DNA for transcription. D.It bends and partly unwinds DNA at a promoter. E.It creates a phosphodiester bond between the nucleotides.

D.It bends and partly unwinds DNA at a promoter.

Genomic DNA in mitochondria A.is inherited from the father. B.is inherited from the mother. C.mostly encodes genes that are needed for its own functions. D.More than one of the above.

D.More than one of the above.

Which of the following is true of RNA compared to DNA? A.RNA and DNA use the same four bases. B.RNA lacks the hydroxyl group on the 2'-carbon atom of its sugar component that DNA has. C.Both RNA and DNA are primarily double stranded. D.RNA molecules are more variable in their secondary structures than DNA molecules. E.RNA is more stable than DNA.

D.RNA molecules are more variable in their secondary structures than DNA molecules.

A mutation in the promoter of an E. coli gene that makes the -10 region a closer match to the consensus would be expected to: A.be an "up" mutation. B.be a "down" mutation. C.improve the binding of RNA polymerase holoenzyme to the promoter. D.both a and c. E.both b and c.

D.both a and c.

Which of the following enzymes creates the phosphodiester bond between adjacent Okazaki fragments? DNA polymerase I DNA polymerase III DNA ligase Topoisomerase More than one of the above

DNA ligase

Which of the following is correct for the one letter amino acid abbreviations for the following polypeptide: alanine, proline, glutamine, glycine, leucine, phenylalanine, arginine,tyrosine, tryptophan, asparagine, lysine A. APYQHNKLFRR B. APYGTRLKFNT C. APGQWNKLFRY D. APGNTRKLYRY E. APQGLFRYWNK

E. APQGLFRYWNK

The following component is NOT required for DNA replication A. Deoxyribonucleotides (dNTP's) B. DNA Polymerase C. Single-stranded DNA (ssDNA) D. Primer E. All of the above are required for DNA replication

E. All of the above are required for DNA replication

Low levels of glucose lead to all of the following, EXCEPT A. cAMP levels increase. B. permease levels increase. C. ß-galactosidase levels increase. D. the lac operon is activated. E. CAP-cAMP loses its affinity for DNA.

E. CAP-cAMP loses its affinity for DNA.

RNA proofreading activity A. Is identical to proofreading activity for DNA except it involves RNA polymerase instead of DNA polymerase. B. Has only been found in some types of eukaryotic cells, primarily fungi. C. Has been recently discovered in E. coli. D. Is critical for proper translation of mRNA. E. Has not been found for any known RNA polymerases

E. Has not been found for any known RNA polymerases

You have created a transgenic mouse that constitutively produces telomerase in all cells. You predict that the these mice will A. have broken, fragmented chromosomes. B. have longer telomeres than wild-type mice of the same age.* C. show no differences when compared to the control animals D. have increased chance of developing cancer.* E. More than one of the above.

E. More than one of the above.

The polytene chromosomes in the salivary glands of the fruit fly,Drosophila melanogaster A. Are much larger than the chromosomes found in the cells of other tissues in the fly. B. Produce high resolution banding patterns that can easily be seen with a light microscope. C. Are unique because their size makes them highly resistant to breakage by X-rays. D. Are extremely fragile and, therefore spontaneously undergo chromosome deletions. E. More than one of the choices A-D are true.

E. More than one of the choices A-D are true.

Which of the following is false regarding tRNA structure and function? A. The enzyme that joins the amino acid to the proper tRNA is called aminoacyl-tRNA synthetase. B. The anticodon of the tRNA is a three nucleotide sequence that base pairs with the corresponding codon of the mRNA. C. Each tRNA has the sequence 5' CCA 3' atthe 3' to which the amino acid is joined. D. During translation, the tRNA with the attached amino acid enters the A site on the ribosome. E. Select this answer if choices A-D are all true.

E. Select this answer if choices A-D are all true.

The lac operon is an example of a negative inducible genetic system because A. It is prokaryotic instead of eukaryotic. B. It requires an inducer (e.g. lactose) that binds directly to the promoter. C. It is derepressed in the presence of the inducer. D. It is repressed in the presence of the inducer. E. The binding of the lac repressor to the operator inhibits transcription by RNA polymerase.

E. The binding of the lac repressor to the operator inhibits transcription by RNA polymerase.

Which of the following is TRUE concerning pre-mRNAs? A.They are larger than the corresponding mature mRNA. B.These RNAs are the precursor molecules for the ribosomal RNA (rRNA). C.These RNAs represent only the 5S rRNA and tRNA precursors. D. They are only found within the nucleus and not the cytoplasm of the cell. E.More than one of the above.

E.More than one of the above.

Which of the following is FALSE concerning the core enzyme and the holoenzyme of prokaryotic RNA polymerase? A.The core enzyme completely lacks RNA polymerase activity. B.Both the core enzyme and the holoenzyme accurately transcribe DNA in vitro. C.The core enzyme has the sigma (s) factor associated with it. D.There is no physical difference between the core enzyme and the holoenzyme. They are just different names for the same protein complex E.Select this answer if all of the above are all false.

E.Select this answer if all of the above are all false.

Which of the following statements is TRUE? An inducible gene is transcribed when the inducer molecule is absent. A repressible gene is controlled by a repressor protein that stimulates transcription. When a structural gene is under negative inducible control, a mutation that causes the repressor protein to be irreversibly bound to the operator will lead to constitutive expression of the operon. For a gene under positive repressible control, transcription of the gene is prevented in the presence of the activator protein. For a gene under positive inducible control, a small inducer molecule is required to allow the activator protein to bind to the DNA.

For a gene under positive inducible control, a small inducer molecule is required to allow the activator protein to bind to the DNA.

Enhancer sequences Have only been found, thus far, in prokaryotic cells. Do not actually stimulate transcription. Rather, they function to help stabilize the mRNA. Increase the efficiency of transcription by directly interacting with RNA polymerase. Have a highly conserved consensus sequence. Have been found both upstream and downstream of the promoter.

Have been found both upstream and downstream of the promoter.

Ribozymes are RNA molecules that Catalyze the synthesis of ribosomes. Remove exons from pre-mRNA in the nucleus of eukaryotic cells. Add amino acids to the corresponding tRNA molecules. Have true catalytic activity. Select this answer if none of the choices A-D are true.

Have true catalytic activity.

Which of the following statements is false? In bacterial cells, the nucleotide sequence of the "sense" strand of DNA matches the nucleotide sequence in the corresponding mRNA transcript except the RNA contains uracil instead of thymine. RNA is a linear polymer of ribonucleotides joined by phosphodiester bonds. Initiation of transcription by RNA polymerase requires a primer. DNA replication is semi-conservative, each new DNA helix contains one old and one newly synthesized strand of DNA. Select this answer if more than one of the choices A-D are false.

Initiation of transcription by RNA polymerase requires a primer.

The product of the lacZ gene Induces expression of the lac operon in the presence of both glucose and lactose. Induces expression of the lac operon when lactose is absent, but glucose is present. Is called the lac repressor, which binds to the operator region in the absence of lactose. Is required for transport of lactose across the cell membrane. Is -galactosidase, which is required for the breakdown of lactose and formation of allolactose.

Is -galactosidase, which is required for the breakdown of lactose and formation of allolactose.

The base in the wobble position of a codon Is the first (5') base. Is the third (3') base. Is complementary to the third base of the anticodon. Both "B" and "C" are correct. None of the choices A-C are correct.

Is the third (3') base.

The TATA-binding protein (TBP) binds to the TATA box sequence in eukaryotic promoters. What is its function in transcriptional initiation? It blocks access of RNA polymerase to the promoter, until removed by general transcription factors. It is required for release of the sigma subunit. It modifies histones so nucleosomes can be removed from DNA for transcription. It bends and partly unwinds DNA at a promoter. It recognizes the promoter for genes transcribed by RNA Polymerase III.

It bends and partly unwinds DNA at a promoter.

Supercoiling of DNA results from overwinding the DNA to create __________ supercoiling or underwinding to create __________ supercoiling. Positive, positive Negative, negative Positive, negative Negative, positive Select this answer if none of the choices A-D are correct.

Positive, negative

Which of the following is not required for replication and stable inheritance in eukaryotic chromosomes? RNA Polymerase II Centromeres Telomeres Origins of replication Choose this answer if all of the choices A-D are required.

RNA Polymerase II

Which of the following statements regarding transcription is true? RNA is only synthesized in a 5' 🡪 3' direction. Transcription requires the association of ribosomes with messenger RNA. RNA polymerase uses the "sense" strand of DNA as a template during transcription. RNA synthesis can proceed in either a 5' 🡪 3' direction or 3' 🡪 5', depending on which DNA strand is used as a template. Select this answer if none of the statements A-D are true.

RNA is only synthesized in a 5' 🡪 3' direction.

Which of the following major classes of RNA in eukaryotic cells is not properly paired with the location in the cell where it carries out its cellular function? Ribosomal RNA (rRNA) is found in the nucleus. Transfer RNA (tRNA) is found in the cytoplasm. Small nuclear RNA (snRNA) is found in the nucleus. Small nucleolar RNA (sno RNA) is found in the nucleolus. Select this answer if all of the choices A-D are properly paired.

Ribosomal RNA (rRNA) is found in the nucleus.

Eukaryotic mRNAs are capped at the 5' end. Which of the following is FALSE concerning this "cap" structure? A guanine nucleotide forms an unusual bond that has a 5' to 5' linkage with three phosphates instead of the usual phosphodiester bond. A methyl (-CH3) group is added to 7-nitrogen of the guanine that forms the cap. The cap structure is required for translation. Capped mRNAs frequently also have a methyl group added to the 2'-OH on the ribose sugar of base attached to the cap nucleotide. Select this answer if choices A-D are all true concerning the 5' cap.

Select this answer if choices A-D are all true concerning the 5' cap.

The most notable feature(s) distinguishing termination of RNA transcripts requiring the rho factor from those that are rho-independent is the presence of An inverted repeat followed by a string of uridine (U) residues in RNAs that terminate without the rho factor.* An inverted repeat followed by a string of uridine (U) residues in RNA that require the rho factor. A series of deoxyadenosine (A) nucleotides in the DNA strand used as a template by RNA polymerase where termination is rho-independent. Poly(U) polymerase that enzymatically adds the poly(U) tail to rho-independent transcripts.* Select this answer if more than one of the choices A-D are correct.

Select this answer if more than one of the choices A-D are correct.

Which of the following is false concerning the telomeres of eukaryotic chromosomes? The telomeres are composed of numerous long (usually 1,000-2,000 bp) repeating DNA sequences. Stimulators of telomerase activity are being investigated as possible anticancer therapeutics.* Telomerase activity is typically active in rapidly dividing cells and in many cancer cells. Telomeres are the structures that surround the centromere of a eukaryotic chromosome.* Select this answer if more than one of the choices A-D are false.

Select this answer if more than one of the choices A-D are false.

Which of the following is true concerning RNA polymerase from E. coli? The complete enzyme (holoenzyme) is a complex composed of six polypeptide subunits.* The core enzyme contains the sigma subunit. In vitro, the core enzyme synthesizes RNA, but does not initiate transcription at the correct place on the DNA template.* Alternative sigma subunits are used by the cell to transcribe specific sets of genes under adverse conditions such as thermal stress ("heat shock").* Select this answer if more than one of the choices A-D are true.

Select this answer if more than one of the choices A-D are true.

Suppose you have identified a segment of genomicgenomic DNA that contains the YFG locus. How DNA that contains the YFG locus. How many many possiblepossible reading frames are there for the reading frames are there for the ORF of the mRNA?

Six (6) Initially, you do not know which strand is the sense strand for the YFG gene. Each strand has 3 possible reading frames. Therefore, there are 6 possible reading frames until the sense strand is established.

In an R-looping experiment, single-stranded DNA from a gene of interest was hybridized to mRNA that was isolated from the cytoplasm of human cells. A single smooth uninterrupted DNA/RNA hybrid was observed using the electron microscope. This indicates that The gene probably contains only one intron. The gene probably does not contain an intron. The gene probably contains several exons. The gene probably contains at least two introns. The hybridization conditions were NOT favorable for annealing the DNA and RNA molecules.

The gene probably does not contain an intron

The Shine-Dalgarno consensus sequence functions as The location on the 5' untranslated region (5'UTR) of a bacterial mRNNA where the small ribosomal subunit associates with the mRNA. The signal for RNA polymerase to terminate transcription in eukaryotic cells. The site for spliceosome splicing of pre-mRNA into mature mRNA in eukaryotic cells. The attachment site for the 7-methyl-guanosine "cap" on the 5' end of eukaryotic mRNAs. The acceptor site for addition of the proper amino acid to the tRNA.

The location on the 5' untranslated region (5'UTR) of a bacterial mRNNA where the small ribosomal subunit associates with the mRNA.

C-value refers to The fraction of cytosine residues in eukaryotic nuclear DNA. The total mass of DNA in the haploid genome of a specific species. The unusual buoyant densities (determined by CsCl density gradient centrifugation) of nuclear DNA from certain eukaryotic species. The mass of DNA found within the chloroplasts of green plants. Select this answer if none of the choices A-D are correct.

The total mass of DNA in the haploid genome of a specific species.

What is the function of eukaryotic RNA polymerase II? Transcription of genes encoding ribosomal RNA. Transcription of genes resulting in messenger RNA. Transcription of genes encoding transfer RNA. Transcription of genes encoding small nuclear RNA. Initiation of transcription, but not elongation.

Transcription of genes resulting in messenger RNA.

When the translation machinery encounters a "stop" codon: Special "stop" tRNAs that lack an amino acid recognize the stop codon. Translation is terminated by release factors (proteins) that recognize the stop codon. Translation terminates because the small ribosomal subunit dissociates and is targeted for proteolytic degredation. It triggers addition of a poly(A) tail to the mRNA. The 5' cap is removed, destabilizing the translation complex.

Translation is terminated by release factors (proteins) that recognize the stop codon.

In E. coli, a mutation that leads to an increased transcription rate of the affected gene and results in closer match to the -10 box (TATA Box) consensus sequence is called a(n) Down mutation Up mutation Consensus mutation Constitutive mutation Phenotypic mutation

Up mutation

The lariat-shaped intermediate that forms during the removal of an intron is due to formation of phosphodiester bonds with an "A" located about 30 nucleotides upstream of the 3' end of the intron. This "A" has and extra phosphodiester bond on the __________ carbon. 5' 3' 1' 2' 4'

2'

Occasionally DNA polymerase III will add an incorrect nucleotide to the end of a growing DNA chain. The presence of a mismatched nucleotide will activate the polymerase's __________, which is one type of proofreading. Mismatch repair system 5' to 3' exonuclease 3' to 5' exonuclease Restriction endonuclease Select this answer if none of the choices A-D are correct.

3' to 5' exonuclease

If instead of 20 amino acids there were 200 amino acids, what would you predict would be the minimum number of bases in a codon?

4^4= 256 possible codons Four (4)

Suppose you found a naturally occurring mRNA composed of alternating C and U residues. Which of the following peptides could be formed? The codons for leucine are CUX and the codons for serine are UCX where X is any ribonucleotide. A. A polypeptide containing alternating leucine and serine residues. B. A polypeptide containing either leucine or serine residues. C. A polypeptide containing only leucine residues D. A polypeptide containing only serine residues E.Cannot be determined from the information provided.

A. A polypeptide containing alternating leucine and serine residues.

Attenuation does not occur in eukaryotes because A. The nuclear membrane that does not allow coupled transcription and translation. B. Eukaryotes only synthesize monocistronic mRNA. C. Attenuation is unique to amino acid synthesis, and eukaryotic cells do not synthesize some amino acids. D. Eukaryotic genes do not have well defined transcriptional termination signals. E. Of the various forms of mRNA processing required prior to translation.

A. The nuclear membrane that does not allow coupled transcription and translation.

Introns are characterized by which of the following invariant consensus sequences? A.5' GU-intron-AG B.5' CG-intron-CG C.5' GU-intron-UA D.5' GU-intron-UG E.5' UU-intron-GG

A.5' GU-intron-AG

Jr. Scientist has identified sequences on an mRNA from a vampire bat that she thinks are important for proper association of the mRNA with a ribosome. These sequences must be part of which portion of the mRNA? A.5' Untranslated Region B.3' Untranslated Region C.Intron D.Open-Reading Frame (ORF) E.None of the above

A.5' Untranslated Region

Which of the following statements is FALSE? A.For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA. B.An inducible gene is transcribed when a specific substance is present. C.A repressible gene is controlled by a regulatory protein that inhibits transcription. D.For a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator. E.When a structural gene is under negative inducible control, a mutation that eliminates the repressor protein will cause the structural gene to be constitutively expressed.

A.For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA.

In eukaryotes, transcriptional activator proteins do all of the following EXCEPT: A.form part of the RNA polymerase II holoenzyme. B.bind either the regulatory promoter or enhancer of a gene. C.modify chromatin to make it more open and accessible. D.increase the rate at which transcription is initiated by RNA polymerase II.

A.form part of the RNA polymerase II holoenzyme.

In rho-dependent transcription termination, the rho factor binds to ___________. A.mRNA B.DNA (near the end of the transcribed region) C.RNA polymerase D.sigma subunit

A.mRNA

If the dispersive model of DNA replication had been correct, Meselson and Stahl would have observed that DNA extracted from bacterial cells following a second round of DNA replication in 14N would have been: A.only hybrid density, and somewhat lighter than after one round of replication. B.only hybrid density, and somewhat heavier than after one round of replication . C.of varying densities, spread throughout the gradient. D.all light density because the DNA molecules would have mostly 14N.E.half hybrid density and half light density.

A.only hybrid density, and somewhat lighter than after one round of replication.

Poly(U) is translated into a polypeptide consisting of all phenylalanine. Poly(C) is translated into a polypeptide consisting of all proline. When a random co-polymer of U and C is made, a protein consisting of the four amino acids—leucine, phenylalanine, proline, and serine—is made even though there are eight possible codons. From this finding, it is possible to conclude that A.some of these four amino acids are specified by more than one codon. B.the genetic code must be a triplet code. C.there is only one codon each for phenylalanine and proline. D.there are three different codons for both serine and leucine.

A.some of these four amino acids are specified by more than one codon.

Which of the following is correct for the one letter amino acid abbreviations for the following polypeptide: alanine, proline, glutamine, glycine, leucine, phenylalanine, arginine, tyrosine, tryptophan, asparagine, lysine. APQGLFRYWNK APYGTRLKFNT APGQWNKLFRY APGNTRKLYRY APYQHNKLFRR

APQGLFRYWNK

In E. coli, a mutation that leads to a decreased transcription rate of the affected gene and results in a decreased homology to the -10 box (TATA Box) consensus sequence is called a(n) A. Up mutation. B. Down mutation. C. Constitutive mutation. D. Consensus mutation. E.Phenotypic mutation.

B. Down mutation.

If you radioactively labeled the phosphate between the last ribonucleotide of an exon and the guanosine at the 5'-end of the adjoining intron as shown by underlining and boldface below, the radioactive phosphate would Exon-Gp/GpUp-intron Be part of the mature mRNA. Be part of the lariat structure of the exon. Be joined by a phosphodiester bond to the "A" at the branch point in the intron. More than one of the choices A-C are true. None of the choices A-C are true.

Be joined by a phosphodiester bond to the "A" at the branch point in the intron.

Which of the following is (are) considered a secondary structure of proteins? Hairpins Helix-turn-helix domains Stem-loops Beta-pleated sheets Zinc fingers

Beta-pleated sheets

Which of the following statements is true? DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand. DNA synthesis is conservative on the leading strand and semiconservative on the lagging strand. DNA synthesis is discontinuous on the leading strand. DNA synthesis is continuous on the lagging strand. The two replication forks move in the same direction.

DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.

You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps. You obtain a sample of this bacteria and perform the same kind of experiment that Meselson and Stahl did to determine how the Mars bacteria replicates its DNA. Based on the following equilibrium centrifugation results, what type of replication would you propose for this new bacteria? Conservative Dispersive Semi-conservative Could be either conservative or dispersive, the data cannot distinguish between these two possibilities. Select this answer if none of the choices A-D are supported by the data.

Dispersive

Which of the following mutations in the amino acid sequence would probably have the most detrimental effect on the functionality of the protein? Leucine to valine Lysine to arginine Aspartate to glutamate Alanine to isoleucine Methionine to proline

Methionine to proline

Which of the following statements is false? Most proteins in human mitochondria are encoded by nuclear genes. Yeast and some plants have mitochondrial genomes that are considerably larger than the mitochondrial genome of humans. There are a number of human genetic diseases that tend to occur later in life that are associated with damage to mitochondrial DNA. Mitochondrial DNA in animals is inherited almost exclusively from the mother. Mitochondrial DNA of vertebrates evolves far slower than the nuclear DNA.

Mitochondrial DNA of vertebrates evolves far slower than the nuclear DNA.

Which of the following statements are true concerning regulation of the Trp operon by attenuation? Less powerful activators bind to transcription factors inhibiting translation. The transcript forms a hairpin structure leading to premature termination. The rate of tryptophan synthesis is inversely proportional to concentration of free tryptophan in the cell. An intermittent on and off control of transcription leads to a decreased rate of tryptophan synthesis. More than one of the above.

More than one of the above.

The genetic code is said to be redundant because Most of the amino acids are specified by more than one codon each. The code is nearly identical among prokaryotic and eukaryotic organisms. Some stop codons also specify amino acids. Frameshift mutations rarely affect the amino acid sequence of the polypeptide. Select this answer if none of the choices A-D are correct.

Most of the amino acids are specified by more than one codon each.

Okazaki fragments are Composed entirely of RNA. Completely degraded by the 5' to 3' exonuclease activity of DNA polymerase III. Synthesized only on the lagging strand of DNA. Are synthesized on both the leading and lagging DNA strands. Now known to have been an experimental artifact.

Synthesized only on the lagging strand of DNA.

Which of the following is true concerning DNA replication in bacterial cells when compared to eukaryotic cells? There is one origin of replication on each chromosome of a eukaryotic cell whereas a bacterial chromosome usually has several origins of replication. The rate of DNA synthesis (nucleotides per second) is much faster in bacterial cells than in eukaryotic cells. In eukaryotic cells, a specific origin of replication often initiates DNA replication several times during the same cycle of DNA replication. Bacterial genomes are replicated by a mechanism called "rolling circle replication". Select this answer if more than one of the choices A-D is true.

The rate of DNA synthesis (nucleotides per second) is much faster in bacterial cells than in eukaryotic cells.

During elongation of a polypeptide chain, The tRNA moves from one codon of the mRNA to the next codon. The ribosome moves toward the 3' end of the mRNA. The growing polypeptide chain is passed from the tRNA in the A site to the amino acid present in the P site. tRNAs enter the empty P site. Answers "B" and "C" are both correct.

The ribosome moves toward the 3' end of the mRNA.

In the E. coli RNA polymerase, which polypeptide is responsible to binding to the -10 and -35 consensus sequences? The alpha subunits The beta subunits The sigma factor The licensing factors Single-strand binding protein

The sigma factor

Which of the following is false concerning formation of aminoacyl-tRNA? The reaction is catalyzed by a class of enzymes known as aminoacyl-tRNA synthetases. The "charging" of the amino acid onto the tRNA requires ATP. There is one aminoacyl-tRNA synthetase for each of the 61 sense codons. The amino acid is added to the 3' end of the tRNA. Select this answer if two or more of choices "A-D" are false.

There is one aminoacyl-tRNA synthetase for each of the 61 sense codons.

__________ are a class of enzymes that introduce either single- or double-strand breaks in a DNA molecule, change the relative position of the strands, and then reseal the break(s). The function of these enzymes is to remove underwinding or overwinding of the DNA helix. Ligases Topoisomerases Single-strand binding (SSB) proteins Primases Select this answer if none of the choices A-D are correct.

Topoisomerases