Choose the best answer.
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1 | | Which statement regarding recombination is false? |
| | A) | Recombination creates new combinations of alleles on a chromosome. |
| | B) | Recombination commonly occurs between homologous sequences. |
| | C) | Sister chromatid exchange is a form of recombination. |
| | D) | Gene conversion may occur during recombination. |
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2 | | Crossing over occurs in both mitosis and meiosis. |
| | A) | True |
| | B) | False |
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3 | | Harlequin chromosomes: |
| | A) | Have been used to demonstrate sister chromatid exchange. |
| | B) | Have sister chromatids that stain differently. |
| | C) | Can only exist in prophase or metaphase. |
| | D) | All of the above. |
| | E) | None of the above. |
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4 | | Which of these describes a Holliday junction? |
| | A) | A section of DNA where base pairing is not exact. |
| | B) | A strand of DNA containing genetic material from two different chromosomes. |
| | C) | An interaction of two strands of DNA from homologous chromosomes. |
| | D) | A three stranded DNA structure where single stranded DNA has invaded a double helix. |
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5 | | After isomerization and resolution, the resulting chromosomes are: |
| | A) | Unchanged from the original chromosome. |
| | B) | Nonrecombinant chromosomes with a heteroduplex region. |
| | C) | Recombinant chromosomes with a heteroduplex region. |
| | D) | Recombinant chromosomes without a heteroduplex region. |
| | E) | Harlequin chromosomes. |
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6 | | Considering the steps listed below, identify the correct sequence of events proposed by the double-stranded break model of recombination. I. Strand invasion and D loop formation. II. DNA gap repair synthesis. III. Generation of single stranded DNA segments. IV. Resolution. |
| | A) | I, III, II, IV |
| | B) | III, I, II, IV |
| | C) | III, II, I, IV |
| | D) | IV, III, I, II |
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7 | | The existence of single Holliday junctions is strong support for the Holliday model of recombination. |
| | A) | True |
| | B) | False |
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8 | | What is gene conversion? |
| | A) | A process by which a gene is rendered nonfunctional. |
| | B) | A process that changes an allele to the allele existing on the homologous chromosome. |
| | C) | A process that restores the wild type function of a gene. |
| | D) | A process that creates a new allele of a gene. |
| | E) | None of these. |
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9 | | If double stranded break recombination and DNA gap repair synthesis result in gene conversion, how is the original allele lost? |
| | A) | It isn't, it is merely rearranged. |
| | B) | It is eliminated by DNA repair enzymes. |
| | C) | It is prevented from replication due to selective pressure. |
| | D) | It is digested away after a break within the gene. |
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10 | | By what process is the λ viral DNA inserted into the E. coli chromosome during lysogeny? |
| | A) | Site specific recombination. |
| | B) | Homologous recombination. |
| | C) | Integral ligation. |
| | D) | Strand invasion. |
| | E) | None of these. |
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11 | | Antibodies are: |
| | A) | Proteins produced by the immune system. |
| | B) | Able to bind specifically to a single antigen. |
| | C) | An example of proteins with quaternary structure. |
| | D) | All of the above. |
| | E) | None of the above. |
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12 | | Which of these mechanisms is NOT critical to generation of antibody variability? |
| | A) | Site specific recombination. |
| | B) | Presence of many V and J regions in a single gene. |
| | C) | Imprecise joining at recombination signal sequences. |
| | D) | All of the above. |
| | E) | None of the above. |
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13 | | What λ DNA protein would you expect to be similar in function to RAG1 and RAG2? |
| | A) | Recombinase |
| | B) | Splicease. |
| | C) | Excisionase. |
| | D) | Integrase. |
| | E) | None of these. |
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14 | | Barbara McClintock noted that, in a particular strain of corn, chromosome 9 tended to break at the same site at a relatively high rate. What caused this breakage? |
| | A) | Random double stranded breaks. |
| | B) | Inaccurate excision of a transposable element. |
| | C) | Insertion of a transposable element. |
| | D) | Holliday junctions. |
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15 | | After identification of the first "mutable site", McClintock was able to demonstrate that the element that caused the mutable site was able to move. What was her evidence? |
| | A) | In some offspring from the original strain, the breakpoint was in a different location. |
| | B) | In some offspring from the original strain, the phenotype was no longer mutable. |
| | C) | In some offspring from the original strain, the Ac element had been lost. |
| | D) | Some strains had breakpoints in different locations than other strains. |
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16 | | Which type of transposable element is only found in eukaryotes (not prokaryotes)? |
| | A) | Transposable elements that move by simple transposition. |
| | B) | Transposable elements that move by replicative transposition. |
| | C) | Retrotransposons, which move via an RNA intermediate. |
| | D) | All of these. |
| | E) | None of these. |
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17 | | Simple transposons do not replicate themselves during transposition but they are able to proliferate. How? |
| | A) | They are replicated after excision from the DNA strand, creating extra copies to be inserted at new sites. |
| | B) | Excision is stimulated by DNA repair processes. |
| | C) | These transposons separate into single stranded elements after excision. Insertion of two single strands followed by DNA gap repair effectively duplicates the element. |
| | D) | All of these. |
| | E) | None of these. |
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18 | | Composite transposons can be recognized by which of the following characteristics? |
| | A) | Inverted repeats. |
| | B) | Direct repeats. |
| | C) | Two pairs of inverted repeats flanking an intervening gene. |
| | D) | Two pairs of direct repeats flanking a transposase gene. |
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19 | | What would you predict would happen if the inverted repeats at one end of a composite transposon were involved in simple transposition, rather than the two repeats at the ends? |
| | A) | The rest of the transposon would be eliminated. |
| | B) | The intervening sequence would be "stranded" and no longer able to move. |
| | C) | The second pair of inverted repeats would be highly likely to jump out. |
| | D) | All of these. |
| | E) | None of these. |
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20 | | Which of the following elements would be considered to be a complete transposable element? |
| | A) | An insertion sequence that includes a transposase gene between the inverted repeats. |
| | B) | A composite element that carries an antibiotic resistance gene. |
| | C) | A replicative transposon that includes a reverse transcriptase gene. |
| | D) | A retrotransposon containing long terminal repeats. |
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21 | | Retrotransposons replicate themselves during transposition. |
| | A) | True |
| | B) | False |
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22 | | Which of the following describes the key difference between simple transposition and replicative transposition? |
| | A) | In simple transposition, transposase catalyzes the removal and reintegration of the transposon, while transposase is not involved in replicative transposition. |
| | B) | In simple transposition, a double stranded piece of DNA is moved from one site to another, while in replicative transposition a single strand is moved, leaving a single strand behind. |
| | C) | Simple transposition requires DNA synthesis while replicative transposition does not. |
| | D) | Replicative transposition requires DNA synthesis while simple transposition does not. |
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23 | | In exon shuffling, a new exon may be inserted into a gene via transposition, leading to a protein with a modified function. Which of these statements is most likely to be true? |
| | A) | The new exon is probably inserted into an existing exon. |
| | B) | The new exon changes the reading frame of the original protein. |
| | C) | The new exon is probably inserted into an intron. |
| | D) | All of the above are likely to be true. |
| | E) | None of the above are likely to be true. |
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24 | | In transposon tagging: |
| | A) | Insertion of a transposon randomly inactivates a gene of interest. |
| | B) | Transposable elements are directed to inactivate a specific gene. |
| | C) | Presence of a transposon in a known gene allows the cloning of the transposon. |
| | D) | All of these. |
| | E) | None of these. |
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25 | | Why is transposon tagging easier for X linked genes? |
| | A) | These genes are more likely to have an interesting phenotype. |
| | B) | These genes are hemizygous in males. |
| | C) | The transposon is more likely to insert into sites on the X chromosome. |
| | D) | The X chromosome does not undergo recombination. |
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26 | | In a modification of transposon tagging known as enhancer trapping, reporter gene coding regions with a minimal promoter but no regulatory elements are placed inside a composite transposon, which is then "jumped" into the chromosomes. Activation of the reporter gene in a specific tissue: |
| | A) | Is unlikely to occur due to the flanking elements of the transposon. |
| | B) | Indicates that the transposon has disrupted a gene whose function is critical for correct function of that tissue. |
| | C) | Indicates that the transposon has integrated near tissue specific regulatory elements. |
| | D) | Is likely to be recessive and thus difficult to identify. |
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