All Free Biology MCQs with Answers
Every Biology question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
19844 questions · page 531 of 1985
5301. Restriction enzymes are present in:
- A. Virus
- B. Bacteria
- C. Plasmids
- D. All of the above
Explanation: These are natural enzymes of bacteria, which they use for their protection againstviruses. The restriction enzyme cuts down the viral DNA but does not harm thebacterial chromosome. They are called restriction enzymes because they restrict thegrowth of viruses.
Correct answer: Bacteria5302. The first restriction enzyme was isolated by:
- A. Kary Mullis
- B. Hamilton
- C. Sanger
- D. Maxam
Explanation: In 1970, Hamilton O. Smith, at Johns Hopkins University, isolated thefirst restriction enzyme.
Correct answer: Hamilton5303. Palindromic sequences are present in:
- A. Single phase
- B. Repeated form
- C. Reverse order
- D. Similar order
Explanation: Bacteria produce a variety of restriction enzymes, whichcut the DNA at very specific sites characterized by a specific sequence of four or sixnucleotides arranged symmetrically in the reverse order. Such sequences are knownas palindromic sequences.
Correct answer: Reverse order5304. Number of restriction enzymes discovered so far are:
- A. 200
- B. 300
- C. 400
- D. 500
Explanation: More than 400 restriction enzymes have been isolated.
Correct answer: 4005305. The number of frequently used restriction enzymes are:
- A. 10
- B. 20
- C. 30
- D. 40
Explanation: More than 400 restriction enzymes have been isolated outof which about 20 are frequently used in recombinant DNA technology.
Correct answer: 205306. The commonly used restriction enzyme is:
- A. E.Coli
- B. EcoR11
- C. EcoR1
- D. EcoR111
Explanation: EcoRl, a commonly used restriction enzyme, cuts double-stranded DNA.
Correct answer: EcoR15307. Natural extrachromosomal circular DNA are:
- A. Endonucleases
- B. Restriction enzyme
- C. Plasmids
- D. Phage virus
Explanation: Plasmids are natural extra-chromosomal circular DNA molecules which carry genes forantibiotic resistance and fertility.
Correct answer: Plasmids5308. Which of the followings is not a vector?
- A. pSc 101
- B. pBR-322
- C. EcoR1
- D. Phage virus
Explanation: EcoRl, a commonly used restriction enzyme, cuts double-stranded. It is not a vector.
Correct answer: EcoR15309. The plasmids having resistant gene against tetracycline and ampicillin are:
- A. pSc 101
- B. pBR-322
- C. EcoR1
- D. Phage virus
Explanation: pBR 322 has antibiotic resistancegenes for tetracycline as well as ampicillin.
Correct answer: pBR-3225310. Which of the following phages is use as vector?
- A. Bacteriophage
- B. Lambda phage
- C. T phage
- D. All of the above
Explanation: Besides plasmids, the DNA of bacterial viruses (for example, lambda phage) can also be usedas a vector.
Correct answer: Lambda phage