Recombinant molecules

  1. When discussing the chromosomal DNA of an organism, the term "genomic equivalent" refers to

    the set of genes essentially identical to those of a different organism.

    the amount of DNA necessary to ensure that the DNA contains at least one copy of each gene of the organism.

    the amount of DNA that is packaged into each of the sex cells of a diploid organism.

    a single region of the DNA that is very similar in sequence and genetic function in a different organism.

  2. When attempting to isolate a specific DNA fragment from a complex mix of chromosomal DNA fragments, the "yield problem" is a concept that refers to

    the fact that as a genome increases in size, the yield of any particular DNA fragment represents a decreasing percentage of the total DNA.

    the poor recovery of DNA from a band excised from an agarose gel.

    the observation that complex genomes do not yield well to digestion with restriction endonucleases.

    the fact that as a genome decreases in size, the yield of DNA isolated becomes smaller, making small genomes difficult with which to work.

  3. "Molecular cloning" is a DNA fragment isolation strategy that is dependent on

    the ability to easily purify a specific DNA fragment.

    extrachromosomal propagation of DNA molecules.

    the generation of novel recombinants including DNA fragments from more than one DNA molecule.

    the use of restriction enzymes and DNA ligases.

  4. Molecular vectors are DNA molecules that are

    able to replicate independently of the host chromosome.

    always very small, circular molecules.

    must be able to replicate well in the organism whose DNA will be cloned in the vector.

    are entirely synthetic DNA molecules developed to assist in molecular cloning strategies.

  5. Naturally occurring DNA molecules that have served as the source of the functional genes in vectors include

    no natural gene sequences are present in vectors, since they were assembled from entirely synthetic DNA sequences.

    bacterial plasmids and episomes.

    drug resistance genes originally present in transposons.

    bacteriophage and viruses.

    multiple cloning sites that consist of a small region of DNA containing several adjacent, often overlapping recognition sites for different restriction enzymes.

  6. The replication origins, the DNA sequences that allow vectors to replicate in a cell, are generally

    universal and allow the vector to replicate in a wide variety of hosts.

    have a limited host range determined by the host range of the DNA sequence that was used in the construction of the vector.

    able to efficiently transfer from the first host cell to recieve the vector, rapidly spreading throughout the host culture to amplify the desired recombinant.

    can be caused to amplify and increase their copy number in a bacterial host cell by the addition of certain antibiotics like chloramphenicol.

  7. The insertional inactivation of a vector phenotypic marker is often used to

    allow a vector containing an extra DNA insert to be easily distinguished from a vector containing no added DNA insert.

    allows the selective elimination of host cells that do not contain the vector.

    select recombinant molecules by complementation of a chromosomal gene function.

    select a specific size class of DNA insert to be inserted into a vector.

  8. Vectors derived from the bacteriophage M13 are novel because

    only these vectors produce an infectious, packaged version of the DNA.

    only these vectors are readily identifed in a bacterial host by their conferred antibiotic resistance.

    these vectors can be induced to make a single-stranded copy of one the strands of a cloned DNA fragment insert.

    only these vectors can integrate into the chromosomal DNA and be maintained as an episome, a chromosomal integrate capable of excision and independent replication.

  9. Recombinant molecules that are constructed in vitro can be introduced into host cells by the method of





  10. A gene library for an organism is

    a listing of all possible genes of that organism.

    a collection of all the known derivatives of a particular gene (allelic variations) that occur naturally in an organism.

    a collection of a sufficient number of recombinant molecules to ensure that all genes of a particular organism are present in the collection.

    a collection of a sufficient number of recombinant molecules to ensure that all genes of a particular organism statistically calculated to be present in the collection.

  11. A cDNA library consists of

    a collection of recombinants containing DNA inserts corresponding to the mRNAs purified from an organism.

    a collection of recombinants containing the mRNA molecules purified from an organism.

    a collection of recombinants containing DNA inserts corresponding to all of the genes that might be expressed by an organism.

    a collection of recombinants containing DNA inserts corresponding to all of the RNAs purified from an organism.

  12. The RNA structural difference that allows the easy construction of cDNA libraries from eukaryotic but not most prokaryotic cells is

    the inability of reverse transcriptase to elongate DNA on a primed prokaryotic mRNA template.

    the presence of a 5´ cap structure on eukaryotic but not prokaryotic mRNA's.

    the presence of alternatively spliced eukaryotic RNA molecules.

    the presence of a 3´ poly-A tail on many eukaryotic mRNA's but few prokaryotic mRNA's.

  13. Methods that might be used to screen or serve through a library for a recombinant containing a specific gene include

    complementation analysis.

    phenotypic screening.

    hybridization analysis.

    screening with antibodies against the desired gene product.

  14. The screening procedure in which a hybridization probe is used to examine bacterial transformants for the presence of a specific recombinant is referred to as a

    Southern blot.

    Northern blot.

    Western blot.

    Eastern blot.

    colony blot or plaque lift.

  15. The screening procedure in which an antibody directed against a desired protein is used to examine bacterial transformants for the presence of a specific recombinant is referred to as a

    Southern blot.

    Northern blot.

    Western blot or immunoblot.

    Eastern blot.

  16. Characterization of the recombinant plasmid vector in a bacterial transformant requires that the plasmid be at least partially purified away from bacterial

    chromosomal DNA.




  17. The miniprep or miniscreen procedure, a rapid method of purifying a small amount of plasmid DNA sufficient for restriction enzyme characterization of DNA inserts, takes advantage of which chemical features to preferentially purify plasmid DNA away from bacterial chromosomal DNA?

    The much more rapid reannealing of plasmid DNA when transferred from alkaline to acidic or neutral conditions.

    The presence of RNA in association with the bacterial chromosomal DNA.

    The tendency of denatured DNA to form a precipitate in the presence of acetate and the detergent sodium dodecyl sulfate.

    The preferential precipitation of plasmid DNA by isopropyl alcohol.

  18. In spite of the apparent presence of sufficient numbers of recombinants to statistically ensure that a particular gene should be present in a library, exhaustive screening sometimes fails to identify the desired recombinant. This can be explained because

    the expression protein or RNA products from certain cloned DNA fragments can be lethal to the host cell.

    some DNA fragments are incapable of replication in the host cell.

    some DNA fragments are instable in the host cell and rapidly recombine or degrade to different forms.

    the non-random sequence of DNA may prevent the appearance of some fragments in a library.

  19. The variety of cloning vectors that has been developed allows the molecular cloning and amplification of DNA fragments in

    only bacterial hosts.

    only microbial hosts.

    only animal cells.

    only plant cells.

    a wide variety of both prokaryotic and eukaryotic cells.

  20. In comparison to natural recombination processes, the primary advantages of the methodology called "recombinant DNA" include

    the ability to efficiently recombine DNA from different organisms.

    the ability to rapidly select and applify a desired DNA fragment.

    the ability to isolate a desired DNA fragment away from other, undesired DNA fragments.

    a degree of precision that allows recombination to be directed at the level of individual nucleotide bases.

    ©1999 Attotron Biosensor Corporation
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