Genetics Ch. 20 Homework – Flashcards
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Which of the following DNA sequences is one strand of a restriction enzyme recognition sequence?
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5' GGATCC 3'
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X-Gal is included in the growth medium on which cells transformed with bacterial plasmids are grown. The reason X-Gal is included is to
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identify bacteria that contain a recombinant plasmid.
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Within a six-base DNA recognition sequence, an enzyme that cuts between the 3rd and 4th bases from the 5' end will generate blunt ends.
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True.
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What is the function of restriction endonucleases in bacteria?
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They provide a defense mechanism against infection by viruses.
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Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends."
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False.
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BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not be recognized by this enzyme?
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3′ TCTTAAG 5′.
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Why are filters overlaid with X‑ray film when screening a cDNA library?
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To visualize probe hybridization events.
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Chromosome walking is used mainly to isolate a gene when the sequence of the gene is known.
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False.
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The role of the primers in PCR is _______.
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to define the target region and provide a 3' end that can be extended by taq polymerase.
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If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification?
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40.
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Immediately after the primers have annealed to the target sequence, _______.
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the temperature is raised so that taq polymerase can extend the primers.
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Which of the following molecules is not required for a PCR reaction?
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Ligase.
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The thermostability of Taq polymerase is required during the annealing phase of PCR.
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False.
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What is the purpose of raising the temperature to 90-95°C at the beginning of each cycle of PCR?
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To separate the double-stranded DNA.
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Phage λ can carry larger DNA fragments than plasmids.
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True.
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Which of the following elements is not found in a plasmid?
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Lambda arms.
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A DNA fragment is introduced into the lacZ gene of a plasmid, which also contains a tetracycline resistance gene. What is the appearance of bacteria transformed with this plasmid if they are spread on plates containing tetracycline and Xgal?
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White colonies that are resistant to tetracycline.
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Which enzyme(s) will produce a DNA fragment that contains the entire vgp gene (shown in red) and has "sticky ends"?
Select all that apply.
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HindIII
BamHI
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Which of the following statements about ddNTPs is true?
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They have a hydrogen at the 3′ carbon of the sugar.
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DNA fragments that are 600 bp long will migrate more quickly through a sequencing gel than fragments that are 150 bp long.
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False.
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Which of the following statements about manual Sanger sequencing is true?
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The DNA sequence obtained is complementary to the template strand.
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How are dideoxynucleotides (ddNTPs) structurally different from deoxynucleotides (dNTPs)?
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ddNTPs lack a 3'-hydroxyl group.
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How does this structural difference make ddNTPs valuable in chain-termination methods of DNA sequencing?
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Once ddNTPs are incorporated in DNA, they terminate the chain elongation, thereby allowing multiple fragments of DNA to be formed and analyzed to reveal the base sequence of original DNA.
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If you performed a PCR experiment starting with only one copy of double-stranded DNA, approximately how many DNA molecules would be present in the reaction tube after 25 cycles of amplification?
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33554432
