All Free Biology MCQs with Answers
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19844 questions · page 527 of 1985
5261. DNA polymerase enzyme for PCR is isolated from bacteria, Thermus aquaticus, because:
- A. It can work at high speed
- B. It can withstand high denaturation temperature
- C. It can withstand low denaturation temperature
- D. It can be used again and again
Explanation: DNA polymerase from Thermus aquaticus (Taq polymerase) is thermostable, so it does not denature at the high temperatures (-95 °C) used during the PCR denaturation step.
Correct answer: It can withstand high denaturation temperature5262. By using Taq polymerase in PCR there will be no need to:
- A. Add more enzyme
- B. Interrupt the process to add more enzyme
- C. Interrupt the process
- D. Use high temperature
Explanation: A high temperature is maintained to discourage duplex formation and chain reaction proceeds in which same enzyme is used again and again.
Correct answer: Interrupt the process to add more enzyme5263. PCR is very specific, the targeted DNA sequence can be _ of total DNA sample.
- A. One part in a million
- B. Less than one part in a million
- C. More than one part in a million
- D. Two parts in a million
Explanation: PCR (Polymerase Chain Reaction) is highly specific and can amplify a targeted DNA sequence even if it is present at less than one part in a million of the total DNA sample.
Correct answer: Less than one part in a million5264. In PCR, primers are sequences of 20 bases that are complementary to the bases on either side of the:
- A. Target DNA
- B. DNA polymerase
- C. Primase
- D. RNA polymerase
Explanation: In PCR, primers bind to sequences flanking the target DNA to initiate replication.
Correct answer: Target DNA5265. The second step of PCR technique is:
- A. Heating DNA for one minute to denature
- B. Cooling for two minutes and adding primer
- C. Addition of DNA polymerase and waiting for 1.5 minutes
- D. Recycling
Explanation: The second step of PCR is annealing, where the reaction is cooled so primers can bind to the single-stranded DNA.
Correct answer: Cooling for two minutes and adding primer5266. PCR can create millions of copies of a single gene or any specific piece of DNA quickly in:
- A. Bioreactor
- B. Test tube
- C. Expression system
- D. Petridish
Explanation: PCR amplifies DNA in vitro, meaning it happens in a test tube, not inside cells or dishes.
Correct answer: Test tube5267. The enzyme that seals the foreign piece of DNA into the vector is called:
- A. DNA polymerase
- B. DNA helicase
- C. DNA ligase
- D. DNA primase
Explanation: DNA ligase is the anzyme that joins DNA fragments by forming phosphodiester bonds, effectively sealing a foreign piece of DNA into a vector.
Correct answer: DNA ligase5268. Besides plasmids, the other molecular carrier or vector is:
- A. DNA of bacteria
- B. DNA of plant viruses
- C. DNA of bacterial viruses (bacteriophages)
- D. DNA of animal viruses
Explanation: Bacteriophages, or bacterial viruses, are efficient vectors for introducing genetic material into bacteria due to their natural ability to infect and insert DNA into bacterial calls
Correct answer: DNA of bacterial viruses (bacteriophages)5269. What was discovered by investigators studying the sex-life of the intestinal bacterium Escherichia coli?
- A. Restriction enzymes
- B. Plasmids
- C. DNA ligases
- D. Sticky ends
Explanation: Plasmids were discovered by investigators studying the sex life of the intestinal bacterium Escherichia coli.
Correct answer: Plasmids5270. For preparation of recombinant DNA, the plasmid is cut with the same enzyme which was used for:
- A. Isolation of the gene of interest
- B. Cutting all such plasmids
- C. Cutting any piece of DNA
- D. Cutting extrachromosomal DNA
Explanation: The same restriction enzyme is used to cut both the plasmid and the gene of interest to create compatible onds for ligation.
Correct answer: Isolation of the gene of interest