Genetics Exam 2 practice exam 107 Questions with Verified Answers
In five Hfr strains, each of which was used to build a time-of-entry map, the genes
... [Show More] entered the recipient cells as follows:
Strain 1: S L A C T F
Strain 2: N P F T C A
Strain 3: T F P N U Y
Strain 4: S H Y U N P
Strain 5: U N P F T C
Which of the following represents a correct compilation of these results?
A) S L A C T F P N H C U
B) N P F T S L A C H U T
C) T C A L S P N U Y H
D) U N P F T C A L S T F
E) S L A C T F P N U Y H - CORRECT ANSWER E) S L A C T F P N U Y H
A competent bacterial strain with genes a, b, and c is transformed by a donor bacterial fragment. Cotransformation frequencies for each gene pair are as follows:
a and b 0.04%
a and c 0.02%
b and c 0.0064%
Which conclusion can be definitively made from this data?
A) Genes b and c are farthest apart.
B) Gene order is a, b, then c.
C) Gene a is closer to c than to b.
D) Gene b is closer to c than to a.
E) Cotransformation of b and c is so frequent, they must be one gene. - CORRECT ANSWER A) Genes b and c are farthest apart.
A competent bacterial strain that has the genotype a- b- c+ is transduced with a P1 phage carrying a fragment of donor chromosome with the a+ b+ c- alleles. The following number of transductants were found after screening for the selectable marker a+.
Transductant Genotype
a+ b- c+ 160
a+ b+ c+ 360
a+ b+ c- 460
a+ b- c- 20
Which of the following conclusions is false?
A) The transduction frequency between a and b is 82%.
B) The transduction frequency between a and c is 52%.
C) Gene a and gene b are closer together than gene a and gene c.
D) The gene order is acb.
E) The selected marker screen will inhibit growth of transductants with the genotype a- b+ c-. - CORRECT ANSWER D) The gene order is acb.
Which of the following regarding lateral gene transfer is false?
A) It may occur by conjugation, transformation, or transduction.
B) It facilitates rapid genome evolution.
C) It can convert benign bacteria into pathogens that cause disease.
D) It allows an organism to rapidly acquire whole segments of chromosomes containing multiple genes.
E) It increases the efficiency of antibiotics against normally sensitive strains. - CORRECT ANSWER E) It increases the efficiency of antibiotics against normally sensitive strains.
What term is given to the total genetic information carried by all members of a population?
A) gene pool
B) genome
C) chromosome complement
D) breeding unit
E) race - CORRECT ANSWER A) gene pool
A number of mechanisms operate to maintain genetic diversity in a population. Why is such diversity favored?
A) Homozygosity is an evolutionary advantage.
B) Diversity leads to inbreeding advantages.
C) Genetic diversity may better adapt a population to inevitable changes in the environment.
D) Greater genetic diversity increases the chances of haploidy.
E) Genetic diversity helps populations avoid diploidy. - CORRECT ANSWER C) Genetic diversity may better adapt a population to inevitable changes in the environment.
In a population of 100 individuals, 49% are of the NN blood type. What percentage is expected to be MN assuming Hardy-Weinberg equilibrium conditions?
A) 9%
B) 21%
C) 42%
D) 51%
E) There is insufficient information to answer this question. - CORRECT ANSWER C) 42%
Albinism is an autosomal recessive trait in humans. Assume that there are 100 albinos (aa) in a population of 1 million. How many individuals would be expected to be homozygous normal (AA) under equilibrium conditions?
A) 100
B) 10,000
C) 19,800
D) 980,100
E) 999,900 - CORRECT ANSWER D) 980,100
In small isolated populations, gene frequencies can fluctuate considerably. The term that applies to this circumstance is ________
A) genetic isolation
B) allelic separation
C) natural selection
D) stabilizing selection
E) genetic drift - CORRECT ANSWER E) genetic drift
Assume that a trait is caused by the homozygous state of a gene that is recessive and autosomal. Nine percent of the individuals in a given population express the phenotype caused by this gene. What percentage of the individuals would be heterozygous for the gene? Assume that the population is in Hardy-Weinberg equilibrium.
A)18%
B) 91%
C) 33%
D) 51%
E) 42% - CORRECT ANSWER E) 42%
Assume that in a Hardy-Weinberg population, 9% of the individuals are of the homozygous recessive phenotype. What percentage are homozygous dominant?
A) 49%
B) 91%
C) 51%
D) 18%
E) 42% - CORRECT ANSWER A) 49%
In a population of 10,000 individuals, where 3600 are MM, 1600 are NN, and 4800 are MN, what are the frequencies of the M alleles and the N alleles?
A) M = 0.5; N = 0.5
B) M = 0.6; N = 0.4
C) M = 0.7; N = 0.3
D) M = 0.8; N = 0.2
E) M = 0.4 N = 0.6 - CORRECT ANSWER B) M = 0.6; N = 0.4
A certain form of albinism in humans is recessive and autosomal. Assume that 1% of the individuals in a given population are albino. Assuming that the population is in Hardy-Weinberg equilibrium, what percentage of the individuals in this population is expected to be heterozygous?
A) 49%
B) 81%
C) 25%
D) 18%
E) 98% - CORRECT ANSWER D) 18%
When scientists were attempting to determine the structure of the genetic code, Crick and coworkers found that when three base additions or three base deletions occurred in a single gene, the wild-type phenotype was sometimes restored. These data supported the hypothesis that ________.
A) the code is triplet
B) the code contains internal punctuation
C) AUG is the initiating triplet
D) the code is overlapping
E) there are three amino acids per base - CORRECT ANSWER A) the code is triplet
A class of mutations that results in multiple contiguous (side-by-side) amino acid changes in proteins is probably caused by which of the following type of mutation?
A) frameshift
B) transversion
C) transition
D) base analog
E) recombinant - CORRECT ANSWER A) frameshift
What is the name given to the three bases in a messenger RNA that bind to the anticodon of tRNA to specify an amino acid placement in a protein?
A) protein
B) anti-anticodon
C) cistron
D) rho
E) codon - CORRECT ANSWER E) codon
What is the initiator triplet in both prokaryotes and eukaryotes? What amino acid is recruited by this triplet?
A) UAA; no amino acid called in
B) UAA or UGA; arginine
C) AUG; arginine
D) AUG; methionine
E) UAA, methionine - CORRECT ANSWER D) AUG; methionine
When examining the genetic code, it is apparent that ________.
A) there can be more than one amino acid for a particular codon
B) AUG is a terminating codon
C) there can be more than one codon for a particular amino acid
D) the code is ambiguous in that the same codon can code for two or more amino acids
E) there are 44 stop codons because there are only 20 amino acids - CORRECT ANSWER C) there can be more than one codon for a particular amino acid
What is one particular function that the codons (UAA, UGA, or UAG) serve during protein synthesis?
A) UAA, UGA, and UAG are initiator codons, not termination codons.
B) They allow the mRNA to assume a variety of linear conformations.
C) These triplets cause frameshift mutations, but are not involved in termination.
D) They provide a substrate for the addition of the initiator amino acid.
E) They act in chain termination. - CORRECT ANSWER E) They act in chain termination.
The genetic code is fairly consistent among all organisms. The term often used to describe such consistency in the code is ________.
A) universal
B) exceptional
C) trans-specific
D) overlapping
E) none of the above - CORRECT ANSWER A) universal
The relationship between a gene and a messenger RNA is that ________.
A) genes are made from mRNAs
B) mRNAs are made from genes
C) mRNAs make proteins, which then code for genes
D) all genes are made from mRNAs
E) mRNA is directly responsible for making Okazaki fragments - CORRECT ANSWER B) mRNAs are made from genes
When considering the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA polymerase(s) binds. Which of the following is a common consensus sequence?
A) TATA
B) GGTTC
C) TTTTAAAA
D) any trinucleotide repeat
E) satellite DNAs - CORRECT ANSWER A) TATA
Which of the following contains the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes?
A) 5′-capping, 3′-poly(A) tail addition, splicing
B) 3′-capping, 5′-poly(A) tail addition, splicing
C) removal of exons, insertion of introns, capping
D) 5′-poly(A) tail addition, insertion of introns, capping
E) heteroduplex formation, base modification, capping - CORRECT ANSWER A) 5′-capping, 3′-poly(A) tail addition, splicing
It has been determined that the gene for Duchenne muscular dystrophy (DMD) is more than 2000 kb (kilobases) in length; however, the mRNA produced by this gene is only about 14 kb long. What is a likely cause of this discrepancy?
A) The exons have been spliced out during mRNA processing.
B) The DNA represents a double-stranded structure, whereas the RNA is single-stranded.
C) There are more amino acids coded for by the DNA than by the mRNA.
D) The introns have been spliced out during mRNA processing.
E) When the mRNA is produced, it is highly folded and therefore less long. - CORRECT ANSWER D) The introns have been spliced out during mRNA processing.
An intron is a section of ________.
A) protein that is clipped out posttranslationally
B) RNA that is removed during RNA processing
C) DNA that is removed during DNA processing
D) transfer RNA that binds to the anticodon
E) carbohydrate that serves as a signal for RNA transport - CORRECT ANSWER B) RNA that is removed during RNA processing
If one compares the base sequences of related genes from different species, one is likely to find that corresponding ________ are usually conserved, but the sequences of ________ are much less well conserved.
A) exons; introns
B) introns; exons
C) introns; chaperons
D) chaperons; exons
E) introns; proteins - CORRECT ANSWER A) exons; introns
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.
A) base analogs and frameshift
B) error prone and spontaneous
C) transversions and transitions
D) euchromatic and heterochromatic
E) sense and antisense - CORRECT ANSWER C) transversions and transitions
Mutations that arise in nature, from no particular artificial agent, are called ________.
A) oblique mutations
B) induced mutations
C) spontaneous mutations
D) chromosomal aberrations
E) cosmic mutations - CORRECT ANSWER C) spontaneous mutations
Which of the following name two mutagens that would be classified as base analogs?
A) acridine orange and proflavine
B) ethylmethane sulfonate and ethylmethylketone peroxide
C) ultraviolet light and cosmic radiation
D) 5-bromouracil and 2-amino purine
E) hydroxyurea and peroxidase - CORRECT ANSWER D) 5-bromouracil and 2-amino purine
The classic Hershey and Chase (1952) experiment that offered evidence in support of DNA being the genetic material in bacteriophages made use of which of the following labeled component(s)?
A) phosphorus and sulfur
B) nitrogen and oxygen
C) tritium
D) hydrogen
E) None of the answers listed are correct. - CORRECT ANSWER A) phosphorus and sulfur
The basic structure of a nucleotide includes ________.
A) amino acids
B) tryptophan and leucine
C) base, sugar, and phosphate
D) mRNA, rRNA, and tRNA
E) phosphorus and sulfur - CORRECT ANSWER C) base, sugar, and phosphate
Considering the structure of double-stranded DNA, which kind(s) of bonds hold one complementary strand to the other?
A) ionic
B) covalent
C) van der Waals
D) hydrogen
E) hydrophobic and hydrophilic - CORRECT ANSWER D) hydrogen
If 15% of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine?
A) 15%
B) 30%
C) 35%
D) 40%
E) 70% - CORRECT ANSWER C) 35%
In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?
A) A = C
B) A = G and C = T
C) A + C = G + T
D) A + T = G + C
E) A = G and C = T and A + C = G + T are both true. - CORRECT ANSWER C) A+C = G+T
Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes?
A) double-stranded, parallel, (A + T)/C + G) = variable, (A + G)/(C + T) = 1.0
B) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0
C) single-stranded, antiparallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
D) double-stranded, parallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
E) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C + T) = variable - CORRECT ANSWER B) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0
Which of the following terms accurately describes the replication of DNA in vivo?
A) conservative
B) dispersive
C) semidiscontinuous
D) nonlinear
E) nonreciprocal - CORRECT ANSWER C) Semidiscontinuous
DNA polymerase III adds nucleotides ________.
A) to the 3′ end of the RNA primer
B) to the 5′ end of the RNA primer
C) in the place of the primer RNA after it is removed
D) to both ends of the RNA primer
E) to internal sites in the DNA template - CORRECT ANSWER A) to the 3′ end of the RNA primer
DNA polymerase I is thought to add nucleotides ________.
A) to the 5′ end of the primer
B) to the 3′ end of the primer
C) in the place of the primer RNA after it is removed
D) on single-stranded templates without need for an RNA primer
E) in a 5′ to 5′ direction - CORRECT ANSWER C) in the place of the primer RNA after it is removed
The discontinuous aspect of replication of DNA in vivo is caused by ________.
A) polymerase slippage
B) trinucleotide repeats
C) DNA polymerase only being able to synthesize DNA in a 5′ to 3′ orientation
D) topoisomerases cutting the DNA in a random fashion
E) sister-chromatid exchanges - CORRECT ANSWER C) DNA polymerase only being able to synthesize DNA in a 5′ to 3′ orientation
Structures located at the ends of eukaryotic chromosomes are called ________.
A) centromeres
B) telomerases
C) recessive mutations
D) telomeres
E) permissive mutations - CORRECT ANSWER D) telomeres
A protein is 300 amino acids long. Which of the following could be the number of nucleotides in the section of DNA that codes for this protein? (Remember: DNA is double-stranded.)
A) 3
B) 100
C) 300
D) 500
E) 1800 - CORRECT ANSWER E) 1800
A short segment of an mRNA molecule is shown below. The polypeptide it codes for is also shown:
5′-AUGGUGCUGAAG-3′: methionine-valine-leucine-lysine
Assume that a mutation in the DNA occurs so that the fourth base (counting from the 5′ end) of the messenger RNA now reads A rather than G. What sequence of amino acids will the mRNA now code for? (You do not need a copy of the genetic code to answer the question.)
A) methionine-valine-leucine-lysine
B) methionine-lysine-leucine-lysine
C) methionine-leucine-leucine-lysine
D) methionine-valine-methionine-lysine
E) methionine-methionine-leucine-lysine - CORRECT ANSWER E) methionine-methionine-leucine-lysine
The term peptidyl transferase relates to ________.
A) base additions during mRNA synthesis
B) peptide bond formation during protein synthesis
C) elongation factors binding to the large ribosomal subunit
D) discontinuous strand replication
E) 5′ capping of mRNA - CORRECT ANSWER B) peptide bond formation during protein synthesis
Which of the following are among the major components of prokaryotic ribosomes?
A) 12S rRNA, 5.8S rRNA, and proteins
B) 16S rRNA, 5.8S rRNA, and 28S rRNA
C) 16S rRNA, 5S rRNA, and 23S rRNA
D) lipids and carbohydrates
E) 18S rRNA, 5.8S rRNA, and proteins - CORRECT ANSWER C) 16S rRNA, 5S rRNA, and 23S rRNA
The primary structure of a protein is determined by ________.
A) the sequence of amino acids
B) hydrogen bonds formed between the components of the peptide linkage
C) a series of helical domains
D) pleated sheets
E) covalent bonds formed between fibroin residues - CORRECT ANSWER A) the sequence of amino acids
The secondary structure of a protein includes ________.
A) gamma and delta
B) alpha and gamma
C) α-helix and β-pleated sheet
D) hydrophobic clusters
E) disulfide bridges - CORRECT ANSWER C) α-helix and β-pleated sheet
1. Recall our discussions on homo and heteropolymers used to decipher the genetic code. A synthetic mRNA was produced with the sequence . . GUGUGU . . It specified the incorporation of: [valine and cysteine.] Another mRNA with the sequence . . GGUGGUGGU specified: [glycine, valine, and tryptophan.] Which triplet can definitely be assigned to valine?
a. GUG
b. UGU
c. GGU
d. UGG
e. DUH - CORRECT ANSWER a. GUG
2. The genetic code is degenerate because:
a. it is not the same for all organisms.
b. certain codons code for more than one amino acid.
c. coding errors occur frequently.
d. there are 64 codons, but only 20 amino acids.
e. the genetic code is not degenerate, it is ambiguous. - CORRECT ANSWER d there are 64 codons, but only 20 amino acids
3. The genetic code is said to be unambiguous. If it were ambiguous, this would imply:
a. several triplets code for one amino acid
b. one gene codes for one amino acid e. one gene codes for many proteins
c. one triplet specifies more than one amino acid
d. many genes code for one protein - CORRECT ANSWER c. one triplet specifies more than one amino acid
4. Although rare, mutations in DNA do occur. One such mutation affected a UGA termination codon and changed it to UGG. What effect would this mutation most likely cause?
a. no RNA will be transcribed.
b. the RNA transcribed from this gene will be much longer than normal.
c. no polypeptide will be produced.
d. the polypeptide produced will have extra amino acids.
e. DNA replication will not be turned off at the appropriate location. - CORRECT ANSWER d. the ploypeptide produced will have extra amino acids
5. A strand of DNA with the sequence 5' ATGCCAGGA is transcribed. What will be the sequence of the transcription product?
a. 5' TACGGTCCT
b. 5' AUGCCAGGA
c. 5' UCCUGGCAU
d. 5' TCCTGGCAT
e. 5' UACGGUCCU - CORRECT ANSWER b. 5' UCCUGGCAU
6. The wobble hypothesis says:
a. there is loose pairing between the 5' end of a single codon and the 3' end of more than one anticodon.
b. there is loose pairing between the 5' end of a single anticodon and the 3' end of more than one codon.
c. there is loose pairing between the 3' end of a single anticodon and the 5' end of more than one codon.
d. there is loose pairing between the 3' end of a single codon and the 5' end of more than one anticodon.
e. after several hours in a bar, one will wobble upon departure. - CORRECT ANSWER b. there is loose pairing between the 5' end of a SINGLE ANTICODON and the 3' end of MORE than one CODON
7. The wobble hypothesis is necessary to explain.
a. how the same tRNA can recognize several different codons.
b. why tryptophan has only one codon while leucine has six.
c. how the codon 5' AUG 3' can code for both N formyl methionine and for the regular methionine.
d. how several different codons can code for the same amino acid.
e. why students wobble upon leaving bars after taking a genetics exam - CORRECT ANSWER a. how the same *tRNA* can recognize several different codons
8. Assume the wobble hypothesis does not exist. In order for protein synthesis to occur precisely, what would have to increase in number?
a. DNA molecules.
b. nitrogen bases.
c. tRNA molecules.
d. codons
e amino acids - CORRECT ANSWER c. tRNA molecules
9. The following relationships are known: CGG specifies arginine, GGC specifies glycine and GCG specifies alanine. Based on your knowledge about the genetic code, it would be most likely that CGA specifies______________.
a. arginine
b. glycine
c. alanine
d. proline
e. none of the above; it is a stop codon. - CORRECT ANSWER a. arginine
10. In a prokaryotic organism, a mutation occurs in the fmet tRNA gene producing a nonfunctional fmet tRNA. What effect would this have on the organism?
a. it would have no effect at all.
b. it would place met in the polypeptide instead of f met.
c. it would inhibit formation of the initiation complex.
d. alanine would be the first amino acid in the polypeptide rather than f met.
e. the organism would evolve into a eukaryote. - CORRECT ANSWER c. it would INHIBIT formation of the INITIATION complex
11. What function does the sigma subunit play in RNA polymerase activity?
a. it allows the enzyme to move from the 5' end to the 3' end of DNA.
b. it is necessary for the catalytic activity of the enzyme.
c. it recognizes the terminator sequence.
d. it recognizes and facilitates binding to the promoter.
e. it is the subunit that distinguishes the RNA polymerase for rRNA from the one for tRNA. - CORRECT ANSWER d. it recognizes and facilitates binding to the promoter
12. Promoters in prokaryotes usually have a -35 box. What is the primary function of this sequence?
a. we do not know the function of this segment.
b. it bonds with a rRNA strand of the ribosomal small subunit during the initiation of translation.
c. it is used to identify the chromosome from other genetic material in the cell.
d. it is involved in promoter recognition by RNA polymerase.
e. it is involved in the binding of RNA polymerase to the DNA template. - CORRECT ANSWER d. it is involved in PROMOTER RECOGNITION by RNA polymerase
13. In bacteria, there are specific sequences of interest in promoters. Which of the following is correct with respect to these sequences?
a. the 10 box is associated with recognition, whereas the -35 box is associated with binding.
b. prokaryotic promoters usually have a TATA box and CAAT box, not a -10 or -35 box.
c. most promoters do not have these regions.
d. the -35 box is associated with recognition, whereas the -10 box is associated with binding.
e. promoters act in prokaryotes like enhancers do in eukaryotes in that they promote transcription, but they are not involved
in initiation of transcription. - CORRECT ANSWER d. the -35* box is associated with RECOGNITION, whereas the -10* box is associated with BINDING
14. The initial mRNA transcribed from a prokaryotic gene is approximately the same size as the final transcript, while the transcript from a eukaryotic gene is much smaller in its final version than the original transcript. Why?
a. eukaryotic genes contain information that is not transcribed.
b. prokaryotic proteins are all smaller than eukaryotic proteins.
c. eukaryotic genes include information for tRNA and rRNA which are not specified by prokaryotic genes.
d. eukaryotic genes contain sequences that are transcribed but not translated.
e. prokaryotic genes are nested, so sometimes a smaller gene is transcribed, rather than the larger one. - CORRECT ANSWER d. eukaryotic genes contain sequences that are transcribed but not translated
15. Which of the following is involved in the initial binding of mRNA to the small ribosomal subunit in prokaryotes?
a. inverted G on 5' end.
b. fmet tRNA
c. Shine Dalgarno sequence
d. RNA polymerase II
e. DNA ligase - CORRECT ANSWER c. Shine-Dalgarno sequence
16. What is the function of the poly A tail of a mRNA?
a. it greatly retards degradation of the strand.
b. it is involved in the termination of translation since AAA is a termination codon.
c. it is involved in the specific binding of the mRNA to the ribosome to initiate translation.
d. it is simply an archaic remnant of molecular processes that were needed prior to evolving into eukaryotes.
e. it really has no known function, but is simply there. - CORRECT ANSWER a. it greatly retards degradation of the strand
17. An E. coli strain was found that had a mutation in the aminoacyl synthetase enzyme that charges the tRNA for formyl methionine (f met). Instead of adding f-met to the appropriate tRNA, the enzyme added alanine instead. What effect would this have on protein synthesis for E. coli?
a. no protein synthesis would take place.
b. because of the wobble hypothesis, only some of the alanine amino acids would be replaced by f met.
c. the original protein would have twice as much alanine as normal proteins.
d. the original protein would have alanine in place of f met at the beginning of the protein
e. protein synthesis would continue beyond the normal stopping point, producing a much longer protein than normal. - CORRECT ANSWER d. the original protein would have alanine in place of f-met at the beginning of the protein
18. We discussed how transfer RNA's undergo substantial post transcriptional base modification. Which of the following is correct relative to this phenomenon?
a. most of the bases in the stems are changed such that they can no longer base pair with each other.
b. bases in the anticodon are always replaced with rare or unusual bases.
c. without base modification a tRNA will not function.
d. bases in the 3' tail are highly modified so they can be recognized by certain codons.
e. base modification prevents a tRNA from functioning. - CORRECT ANSWER c. WITHOUT base modification a tRNA will NOT FUNCTION
19. RNA polymerase III promoters are unique in that they:
a. only transcribe mRNA genes.
b. are located within the gene sequence rather than upstream from the gene.
c. only transcribe hnDNA.
d. are only found in prokaryotic organisms.
e. have the consensus Pribnow sequence that is usually found in prokaryotes. - CORRECT ANSWER b. are LOCATED WITHIN the gene sequence rather than upstream from the gene.
20. For which eukaryotic polymerase does each species have it's own distinct promoter sequence?
a. RNA polymerase I
b. RNA polymerase II
c. RNA polymerase III
d. DNA polymerase I
e. DNA polymerase II - CORRECT ANSWER a. RNA polymerase I
21. In bacteria, RNA polymerase is composed of two functional units. Which of the following is correct with respect to the function of this molecule?
a. the core enzyme is responsible for the catalytic activity of the enzyme.
b. the sigma unit is an important component of RNA polymerase II.
c. the core enzyme facilitates recognition and binding to the DNA template.
d. the sigma unit is responsible for the catalytic activity of the enzyme.
e. this is a trick question since bacteria don't have any RNA polymerase molecules. - CORRECT ANSWER a. the CORE enzyme is RESPONSIBLE for the CATALYTIC ACTIVITY of the enzyme
22. In gene promoters, there are specific sequences of interest (well they are to some people). Which of the following is correct with respect to these sequences?
a. the 10 box is associated with template binding in eukaryotes.
b. prokaryotic promoters usually have a CAAT box, but not a GC box.
c. the TATA box is associated with template binding in eukaryotes.
d. the 35 box is associated with recognition in eukaryotes.
e. the CAAT box is associated with template binding in prokaryotes. - CORRECT ANSWER c. the TATA box is associated with template binding in eukaryotes
23. In eukaryotes, hnRNA's also known as pre mRNA's undergo an elaborate processing. Which of the following is correct with respect to this process?
a. an inverted guanine residue is added which then interacts with charged tRNA's during translation.
b. all exon sequences are cleaved from the RNA strand.
c. the adenylated tail inhibits rapid degradation of the mRNA.
d. all intron sequences are translated to produce the polypeptide.
e. the Shine Dalgarno sequence is added to the 5' end of the strand to facilitate binding to the ribosome. - CORRECT ANSWER c. the ADENYLATED TAIL INHIBITS rapid DEGRADATION of the mRNA
24. An intron is:
a. a segment of DNA whose transcription product is translated into a polypeptide.
b. a segment of spacer DNA located between genes in the prokaryotic genome.
c. a segment of DNA whose transcription product is translated into the part of a polypeptide that is excised.
d. a segment of DNA where the RNA polymerase attaches to begin transcription.
e. a segment of DNA within an eukaryotic gene that never gets translated into protein. - CORRECT ANSWER e. a segment of DNA within a eukaryotic gene that never gets translated into protein
25. There is several nucleic acid molecules involved in polypeptide synthesis, however, only one is physically connected to an amino acid. Which one is this?
a. mRNA
b. rRNA
c. tRNA
d. hnRNA
e. one of the above (technically correct, but worth nothing!) - CORRECT ANSWER c. tRNA
26. Transfer RNAs that do not contain rare (unusual) bases:
a. do not function.
b. have an abnormal cloverleaf structure.
c. function normally.
d. can bind to amino acids, but not mRNA.
e. are very dull molecules. - CORRECT ANSWER a. DO NOT function
27. A particular tRNA was known to be 90 nucleotides in length and a mRNA was 300 nucleotides in length. Assume that f methionine, the initiator, is hydrolyzed off and that only the last codon is a terminator. If these RNA's were involved in a system actively synthesizing protein, what would be the number of amino acids in the functional protein synthesized?
a. 98
b. 300
c. 90
d. 88
e. 30 - CORRECT ANSWER a. 98
28. In our discussion of the genetic code, we learned that three codons are known as termination or stop codons. How many tRNA's normally recognize these codons?
a. 0
b. 1
c. 2
d. 3
e. 32 - CORRECT ANSWER a. 0
29. We have frequently discussed the complementary nature of nucleic acid strands. Which of the following sequences show complementarity between them?
a. codon and partner DNA.
b. template DNA and anticodon.
c. anticodon and partner DNA.
d. partner DNA and mRNA transcript.
e. all of the above. - CORRECT ANSWER c. anitcodon and partner DNA
30. The Shine Dalgarno sequence:
a. is complimentary to promoter regions.
b. is responsible for termination of translation.
c. is complimentary to 3' end of the 16S rRNA strand.
d. is responsible for termination of transcription.
e. is yet another feeble attempt for scientists to spread their fame by naming an esoteric entity after themselves. - CORRECT ANSWER c. is complimentary to 3' end of the 16S rRNA strand
31. _________ catalyses the formation of the peptide bond linking two amino acids during translation.
a. elongation factor proteins.
b. aminoacyl synthetase.
c. charged tRNA.
d. peptidyl transferase.
e. aminolinkage synthetase. - CORRECT ANSWER d. peptidyl transferase
32. Identify the correct sequence of steps in protein synthesis.
A peptide bond formation
B binding of fmet tRNA to mRNA ribosome complex
C binding of mRNA to ribosome
D release of fmet tRNA and translocation
E binding of charged tRNA to A site
a. A, B, C, D, E.
b. C, B, E, A, D.
c. B, C, E, A, D.
d. C, B, A, E, D.
e. C, A, E, D, B. - CORRECT ANSWER C (binding of mRNA to ribosome)
B (binding of fmet-tRNA to mRNA-ribosome complex)
E (binding of charged tRNA to A site)
A (peptide bond formation)
D (release of fmet-tRNA and translocation)
33. The genetic code contains 61 codons that specify twenty amino acids. Recall that the initiator codon is always AUG and the three stop codons are UAA, UGA, and UAG. Given the following 3' to 5' DNA sequence, which numbers would correspond to the beginning and end of translation?
AAA AGA ATA ACA GAG GGG GTG GCG TAC TAA GAG GCG TCC CGG GTA TTT ATC GCC
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
a. 1 and 18
b. 9 and 17
c. 6 and 12
d. 5 and 17
e. 10 and 15 - CORRECT ANSWER b. 9 and 17
34. The correct sequence of events involving a given amino acid in protein synthesis is:
1 pairing of charged tRNA with mRNA
2 binds with aminoacyl synthetase
3 peptide bond formation.
4 attached to tRNA
a. 1, 2, 3, 4
b. 4, 3, 2, 1
c. 2, 4, 1, 3
d. 4, 2, 1, 3
e. 3, 4, 1, 2 - CORRECT ANSWER 2 (binds with aminoacyl synthetase)
4 (attached to tRNA)
1 (pairing of charged tRNA with mRNA)
3 (peptide bond formation)
35. How could you determine the number of amino acids in a polypeptide that was synthesized by a bacterial cell?
a. you would need to know how many amino acids are available in the bacteria.
b. you would need to know how many introns the gene has in order to determine polypeptide length.
c. you would need to know how many bases are in the template strand; from this you could closely approximate the number of amino acids.
d. you would need to know how many tRNA's are found in the species in order to determine the number of amino acids.
e. you would need to know how many genes were active at the same time as this would determine if sufficient
ribosomes are available for translation. - CORRECT ANSWER c. you would need to know HOW MANY BASES are in the template strand; from this you could closely approximate the number of amino acids
36. A mad cartoonist has all the molecules necessary for protein synthesis in a test tube. He has inadvertently mixed up some of the components. Included in his test tube are: partner DNA from Fred Flintstone, tRNA molecules from Bugs Bunny, ribosomes from Tweety Bird, mRNA from George Jetson, and amino acids from Wiley Coyote. Assuming this concoction is functional and translation occurs, the first proteins generated will be the same proteins produced by which of the above mentioned critters?
a. Bugs Bunny
b. Fred Flintstone
c. Tweety Bird
d. George Jetson
e. Wiley Coyote - CORRECT ANSWER d. mRNA from George Jetson
37. There are four different codons for phenylalanine. How many aminoacyl synthetase enzymes recognize this amino acid?
a. 1
b. 3
c. 20
d. 0
e. billions and billions (answer submitted by the estate of the late C. Sagan) - CORRECT ANSWER a. 1
38. Identify the correct sequence of steps in protein synthesis in prokaryotes:
A binding of large ribosomal subunit to initiation complex
B peptide bond formation
C binding of mRNA to small subunit of ribosome
D binding of charged tRNA to A site
E release of fmet tRNA and translocation
a. E, B, C, A, D
b. C, A, D, B, E
c. B, C, A, D, E
d. C, E, B, A, D
e. A, B, C, D, E - CORRECT ANSWER b
C (binding of mRNA to small subunit of ribosome)
A (binding of large ribosomal subunit to initiation complex)
D (binding of charged tRNA to A site)
B (peptide bond formation)
E (release of fmet-tRNA and translocation)
39. A very odd life form is found in a cave in Kentucky. Compared to all other biological systems, this critter has a different number of amino acids and a different number of nucleotides. In research to determine the number of nucleotides necessary to specify a single amino acid, proflavin was used to induce frameshift mutations. When one, two or three nucleotides were added to a nucleotide sequence, the resultant polypeptide chains were all similar to the original polypeptide chain. What does this suggest about the number of nucleotides that specify a single amino acid?
a. 1 nucleotide specifies 1 amino acid.
b. 2 nucleotides specify 1 amino acid.
c. 3 nucleotides specify 1 amino acid.
d. 4 nucleotides specify 1 amino acid.
e. 5 nucleotides specify 1 amino acid - CORRECT ANSWER a. 1 nucleotide specifies for one amino acid
40. What work directly demonstrated the consequences that can be due to a single amino acid change?
a. work on imaginal eye disk in fruit flies.
b. work on sickle cell anemia in humans.
c. work on vitamin deficiencies in molds.
d. work on eye mutants in Drosophila.
e. work showing genetics instructors are really mutant life forms. - CORRECT ANSWER b. work on sickle cell anemia in humans
41. The primary structure of a protein represents:
a. it's amino acid sequence.
b. it's functional configuration.
c. the subunits of a protein.
d. it's pleated sheet.
e. it's alpha helix. - CORRECT ANSWER a. its amino acid sequence
42. The tertiary structure of a protein is:
a. the amino acid sequence of the protein.
b. the result of spiraling of the polypeptide due to the formation of hydrogen bonds.
c. the initial product of transcription.
d. a complex consisting of two or more polypeptides.
e. the three dimensional conformation of the polypeptide chain. - CORRECT ANSWER e. the three dimensional conformation of the polypeptide chain
43. Amino acids are linked together by peptide bonds and are the building blocks of proteins. Which of the following represents the components of an amino acid?
a. amino group and ribose sugar.
b. amino group and carboxyl group.
c. amino group, carboxyl group and radical group.
d. amino group and peptide group.
e. amino group, carboxyl group and conservative group - CORRECT ANSWER c. amino group, carboxyl group, and radical group
44. The reason why the information stored in most genes is not constantly expressed is that:
a. the life span of a gene is short.
b. there are regulatory mechanisms that turn genes off and on depending on the cells' need.
c. the cells get tired.
d. the genetic information of a gene is expressed only once in the lifetime of the organism.
e. the information is destroyed in the long run. - CORRECT ANSWER b. there are regulatory mechanisms that turn genes off and on depending on the cells' need
45. A structural gene may be defined as:
a. a sequence of RNA which catalyzes the formation of peptide bonds.
b. a sequence of DNA which codes for the amino acid sequence of a polypeptide.
c. a gene whose gene product is a component of the large subunit of the ribosome.
d. a sequence of DNA which is involved in promoter recognition by RNA polymerase.
e. a gene that is involved in the formation of the double helix structure of a DNA molecule. - CORRECT ANSWER b. a sequence of DNA which codes for the amino acid sequence of a polypeptide
46. An operator is:
a. a DNA segment involved in the translation of polypeptides.
b. a DNA segment that is part of the promoter.
c. a DNA segment which assists RNA polymerase in binding to the promoter.
d. a DNA segment that serves a regulatory function in the control of transcription.
e. an individual of few, if any, scruples (AKA as a presidential candidate). - CORRECT ANSWER d. a DNA segment that serves a REGULATORY FUNCTION in the control of transcrption
47. In the functioning of the lac operon, an inducer substance binds to:
a. the operator, causing an allosteric shift which initiates transcription.
b. a repressor protein, which then dissociates from the operator.
c. lactose, which binds to DNA and completes transcription of the structural genes.
d. a repressor protein, causing it to bind tightly to the operator.
e. the promoter, which initiates transcription. - CORRECT ANSWER b. a REPRESSOR protein, which then DISSOCIATES from the OPERATOR
48. The lac operon is:
a. inducible and under positive control.
b. repressible and under positive control.
c. inducible and under negative control.
d. repressible and under negative control.
e. found in E. coli (technically correct but worth zilch on this exam). - CORRECT ANSWER c. inducible under negative control
49. With regard to the lac operon, the repressor protein normally:
a. binds to a structural gene when lactose is abundant.
b. binds to the promoter when lactose is abundant.
c. binds to the operator when lac is abundant.
d. binds to a lac molecule when lactose is rare.
e. binds to the operator when lactose is rare. - CORRECT ANSWER e. binds to the OPERATOR when lactose is RARE.
50. A mutation occurred in the repressor protein gene of the lac operon. The protein produced by this mutant gene is not capable of binding to the operator. This would result in:
a. the structural genes never being transcribed.
b. the operon being classified as a repressible system.
c. the structural genes always being transcribed.
d. the operon being classified as a positive control system.
e. a bacterial strain capable of growing in Lake Alice. - CORRECT ANSWER c. the structural genes ALWAYS being transcribed
51. Although rare in nature, mutations occur frequently on genetic exams. One such mutation occurred in the repressor protein gene of the lac operon. The repressor protein from this mutated gene did not have a lactose binding site. Which of the following would be correct for this mutated bacterium?
a. the structural genes of the operon would never be transcribed.
b. the structural genes of the operon would be constantly transcribed.
c. the lac operon would become a repressible operon.
d. the bacteria would always break down lactose even in the absence of lactose.
e. the bacteria would synthesize lactose since it cannot degrade it. - CORRECT ANSWER a. the structural genes of the operon would NEVER be transcribed
52. Which of the following represents the role of glucose in the catabolite repression system?
a. glucose interferes with the CAP site allowing transcription to occur.
b. glucose interferes with the CAP protein inhibiting transcription of the structural genes.
c. glucose interferes with adenyl cyclase preventing it from producing cAMP.
d. glucose interferes with the polymerase site of the promoter inhibiting RNA polymerase binding.
e. glucose has no role in catabolite repression. - CORRECT ANSWER c. glucose interferes with adenyl cyclase preventing it from producing cAMP
53. Glucose is known to regulate the lac operon via catabolite repression. Which of the following is accurate with respect to the effect of glucose?
a. there is no CAP cAMP complex bound to the promoter which greatly decreases transcriptional efficiency.
b. glucose interferes with the CAP protein inhibiting transcription of the structural genes.
c. glucose prevents the formation of beta galactosidase, so no lactose is metabolized.
d. glucose binds to the poly site of the promoter inhibiting RNA polymerase binding.
e. Dr. P is wrong; glucose has no role in catabolite repression. - CORRECT ANSWER a. there is no CAP cAMP complex bound to the promoter which greatly decreases transcriptional efficiency
54. Which of the following is accurate with respect to catabolite repression?
a. it is an inducible system.
b. it is under negative control.
c. it is under positive control.
d. it is regulated by attenuation.
e. it is a system found in bacteria (technically correct but worth zilch) - CORRECT ANSWER c. it is under positive control
55. The biosynthesis of tryptophan in bacteria is regulated by a repressor protein system and a secondary attenuation system. Which of the following is correct with respect to the trp attenuation system?
a. the location of the ribosome relative to the polymerase determines whether transcription continues or is terminated.
b. the availability of charged tRNA trp will determine whether or not transcription continues or is terminated.
c. termination will always be terminated when there is sufficient trp in the cell.
d. the rate of transcription does not decrease due to attenuation, but is actually increased.
e. there is no attenuation of the trp operon in bacteria. - CORRECT ANSWER b. the availability of charged tRNA trp will determine whether or not transcription continues or is terminated
56. The repressor protein in the trp operon normally:
a. binds to the operator when no tryptophan is present.
b. binds to a structural gene when tryptophan is present.
c. binds to the operator when tryptophan is present.
d. binds to a structural gene when no tryptophan is present.
e. binds to the promoter when tryptophan is present. - CORRECT ANSWER c. binds to the OPERATOR when typtophan is PRESENT
57. The trp operon, lac operon, and catabolite repression systems are examples of what types of control?
a. negative; negative; positive.
b. positive; negative; positive.
c. negative; positive; negative.
d. positive; negative; negative.
e. negative; positive; positive. - CORRECT ANSWER a. negative, negative, positive
58. In a certain strain of bacteria, a mutation in the operator gene of the trp operon resulted in a nonfunctional operator region. This would cause the bacterial strain to:
a. never transcribe the structural genes of the operon.
b. become a prototroph.
c. become an inducible system.
d. always break down lactose even in the absence of lactose.
e. constantly transcribe the structural genes of the operon. - CORRECT ANSWER e. CONSTANTLY transcribe the structural genes of the operon
59. In E. coli, trp biosynthesis is regulated by a repressor protein system and a secondary system called attenuation. Which of the following is correct with respect to the trp attenuation system?
a. if the ribosome begins translation before the completion of transcription, transcription will be terminated.
b. if the ribosome stalls at the trp codons an antiterminator hairpin will be formed and transcription will proceed.
c. termination of transcription will always occur if there is no trp present in the cell.
d. the rate of translation will increase due to the attenuation mechanism.
e. attenuation of the trp operon does not occur in prokaryotes, but is found only in eukaryotes. - CORRECT ANSWER b. if the ribosome STALLS at the trp codons an antiterminator hairpin will be formed and transcription will PROCEED.
60. A mutation occurred in a bacterial strain resulting in a nonfunctional trp site in the repressor protein for the trp operon. What effect would this mutation have on this system?
a. the structural genes of the operon would never be transcribed.
b. there would be no regulation of transcription.
c. the only control of transcription would be attenuation.
d. the structural genes of the operon would always be transcribed.
e. the bacteria would die an agonizing death, similar to what you experience taking a genetics exam. - CORRECT ANSWER c. the ONLY control of transcription would be ATTENUATION
61. Certain sequences have been found which enhance the transcription of genes, and are therefore called enhancer sequences. Which of the following is true with respect to these sequences?
a. these sequences are part of promoters recognized by RNA polymerase II.
b. these sequences are never found upstream from the gene.
c. these sequences can be inverted without a loss of activity.
d. these sequences are found only in prokaryotes.
e. these sequences enhance your grade on Genetics exams. - CORRECT ANSWER c. these sequencces can be inverted without a loss of activity [Show Less]