Exam 4 Review
Supplemental Instruction
IowaStateUniversity / Leader: / Matt C.
Course: / Biol/Gen 313
Instructor: / Dr. Myers & Dr. Vollbrecht
Date: / 04/10/2017

Introduction: Chapters 12, 13, and 14 are covered on this exam.

Multiple Choice

  1. After an interrupted mating experiment, you observe the following data reported as time needed to rescue 50% of the auxotrophic colonies. What is the order of the genes on the chromosome?

Gene A / Gene B / Gene C / Gene D / Gene E
Hfr Strain 1 / 10 min / 1 min / 7 min / 3 min / 4 min
Hfr Strain 2 / 4 min / 2 min / 7 min / 11 min / 10 min
Hfr Strain 3 / 7 min / 9 min / 4 min / 1 min / 2 min
  1. B, A, C, D, E
  2. B, D, E, A, C
  3. C, A, B, D, E
  4. C, E, D, A, B
  5. None of the above

  1. You discover a new operon in charge of modifying the sugar xylose. When xylose enters the cell, transcription of this xyl operon begins. A regulator protein involved in this operon becomes bound to the operator after binding to xylose. What is the method of regulation described here?

  1. Positive inducible
  2. Positive repressible
  3. Negative inducible
  4. Negative repressible
  5. Constitutively regulated

  1. Some genes are under control of the galactose-mediated regulation system in yeast. In this system, what is the function of Gal80?
  2. Gal80 is an activator protein that promotes RNA polymerase binding.
  3. Gal80 is an inhibitor that prevents the action of an activator.
  4. Gal80 acts to free a separate activator from inhibition.
  5. Gal80 is a transcriptional mediator and member of the TFIID complex.
  6. Multiple of the above are correct.
  1. In Arabidopsis thaliana, sequence R is involved in the activation of the localized sequences K and H. Sequence U exhibits identical response elements to K and H, but is acted on by the intervening effect of sequence T and is instead only activated by another sequence R that is further downstream. What is sequence T an example of?
  2. Regulatory gene for an activator
  3. Regulatory gene for a repressor
  4. Enhancer
  5. Insulator
  6. Response element
  1. While researching reoccurring gene sequences in Caenorhabditis elegans, you note that in one C. elegans a sequence surrounded by inverted repeats is located at 3 different positions in coding regions of the organism, while in a different sample, the reoccurring element is located in 5 different coding regions. What is the likely explanation for this?
  2. The sequence is the result of duplication.
  3. The sequence is the result of non-reciprocal translocation.
  4. The sequence is transposable.
  5. The sequence is a trinucleotide repeat that develops additional copies due to slippage.
  6. None of the above are good explanations.
  1. What is the purpose of annealing when performing PCR?
  2. The lower temperature allows Taq polymerase to renature after the hotter melting temperature.
  3. The lower temperature allows DNA primers to bind to template strands.
  4. The lower temperature allows Taq polymerase to bind to the primer-template heterodimer.
  5. The lower temperature allows dNTPs to more efficiently enter the polymerase active site and subsequently polymerize.
  6. Multiple of the above.
  1. You observe that a certain transgenic knock-out strain in maize produces an embryo lethal phenotype. You perform a second transgenic insertion to reintroduce a wild-type version of the knocked-out gene, but still observe the lethal phenotype. What most likely explains what has happened, assuming the second insertion was successful?
  2. Complementation has showed that the first transgenic plant’s phenotype is the result of the location of the first insert, not of the knock-out.
  3. Introduction of the wild-type gene has shown that the genotype leading to the lethal phenotype is actual a dominant trait.
  4. Instead of being a result of the knock-out, chromosomal rearrangement has occurred in the first plant line that prevents the formation of gametes.
  5. The addition of the new gene has resulted in an enzyme dosage problem that is also lethal.
  6. None of the above are good explanations.
  1. A series of mutations occurs in a strain of E. coli that you’re studying that results in dramatically overexpressed and super-activated cAMP phosphodiesterases. These enzymes break down any cAMP that the cell can manage to make. What is the likely effect of this on the lac operon?
  2. The lac operon will be constitutively expressed.
  3. The lac operon will produce about half of the usual transcript count.
  4. The lac operon will not be transcribed.
  5. The lac operon will be unaffected.
  6. We can’t tell the effect on the lac operon from this information.
  1. Exposure to UV light can damage the DNA. How does it do this?
  2. UV light causes spontaneous de-acetylation of histones.
  3. UV light causes cytosine methylation.
  4. UV light causes a single-stranded break in the DNA.
  5. UV light causes adjacent thymines to dimerize.
  6. Multiple of the above are methods of action of UV light damage.
  1. You are performing a set of experiments to determine amino acid residues of structural importance in GAPDH2. You perform a single amino acid mutation converting a tyrosine to a phenylalanine and perform an enzyme assay of the mutant enzyme. You note that enzymatic activity matches the wild-type. What sort of mutation has occurred?

  1. Missense
  2. Silent
  3. Loss-of-function
  4. Neutral
  5. Gain-of-function.

  1. Which of the following methods of expression regulation results in the shortest time between initiating regulation and observing a change in expression?
  2. Protein modification
  3. Histone deacetylation
  4. RNA degradation mediated by miRNA
  5. Translational control
  6. Transcriptional regulation
  1. While trying to determine the cause of the infection of a human patient, you isolate reverse transcriptase from infected cells. What is the likely origin of this enzyme?
  2. A bacterial contaminant
  3. Part of the phage ghost
  4. A dsDNA virus
  5. A retrovirus
  6. Contamination of human enzymes
  1. What is the function of lacI?
  2. It is the response element that is acted on to repress the lac operon.
  3. It is a molecule that binds near the lac promoter to physically impede RNA polymerase.
  4. It cleaves lactose into two monosaccharides that can then be metabolized.
  5. It binds to cAMP and represses the lac operon.
  6. None of the above.
  1. An intragenic suppressor mutation occurs in gene V that had previously been affected by a frameshift resulting from a base addition. What could this mutation be?
  2. A base deletion just upstream from the added base.
  3. A base addition just downstream from the previously added base.
  4. A mutation in a gene Y that covers up the gene V mutation.
  5. A crossing over event that pulls away the mutated base.
  6. None of the above.
  1. Which of the below is a cis-acting mutation?

  1. LacP+
  2. LacI-
  3. LacOC
  4. All of the above.
  5. Only a. and c.

  1. Which of the following is/are heritable?
  2. A silent mutation in the gametophyte.
  3. A nonsense mutation in a somatic cell.
  4. Increased cytosine methylation.
  5. All of the above.
  6. Just two of the above.
  1. A single type of signal molecule enters the nucleus of a eukaryotic cell and induces transcription in multiple genes. How does this most likely happen?
  2. The genes are linked on an operon.
  3. Signal integration occurred and expanded the downstream signal.
  4. A first gene was activated by the signal directly and was transcribed, translated, and the resulting product activated the other genes.
  5. The activated genes share response elements.
  6. None of the above.
  1. High levels of tryptophan in the cell induce the trp operon regulator to bind and inhibit transcription. What is the term used to describe tryptophan in this instance?

  1. Attenuator
  2. Activator
  3. Repressor
  4. Inducer
  5. Co-repressor

  1. Which of these structures will is a DNA-binding motif in proteins?
  2. Beta barrels
  3. Coiled coil
  4. Zinc fingers
  5. Greek key
  6. None of the above
  1. Given the following monoploid operons, which would not synthesize lactose permease under any circumstance?
  2. LacI+, LacP+, LacO+, LacZ+, LacY+
  3. LacI-, LacP+, LacO+, LacZ-, LacY+
  4. LacI+, LacP-, LacOC, LacZ+, LacY+
  5. LacIS, LacP+, LacOC, LacZ+, LacY+
  6. None of the above
  1. Which of the following are epigenetic changes that would affect regulation of gene expression?
  2. Histone acetylation
  3. Moving histone complexes along the DNA
  4. Cytosine methylation
  5. All of the above
  6. Just two of the above
  1. Which of the following repeats is most likely to expand during DNA replication?

  1. CAG
  2. TAG
  3. CGG
  4. TAA
  5. Multiple of these

  1. You observe the following part of a chromosome with inverted transposons. Which of the following is most likely to occur?
  1. Inversion of the region between the transposons.
  2. Excision of the region from one transposon to the other due to recombination.
  3. A mutation in the inverted repeat region that renders both transposons immobile.
  4. All of the above are possible and equally likely.
  5. This scenario could never happen.
  1. Given the following partial diploid chromosome of the lac operon, what is the mode of regulation?

LacI-, LacP-, LacOC, LacZ+, LacY+

LacIS, LacP+, LacO+, LacZ+, LacY+

  1. Inducible
  2. Repressible
  3. Constitutive transcription
  4. No transcription
  5. This can’t be determined