All Free Biology MCQs with Answers
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19844 questions · page 524 of 1985
5231. Given are the steps of DNA fingerprinting (southern blot test).I. X-ray film.II. Electrophoresis.III. Radioactive probing.IV. Digestion with restriction enzyme.The CORRECT sequence in which these steps are followed is:
- A. IV→III→ II→ I
- B. III→ IV→ I→ II
- C. IV→ II→ III→ I
- D. I→ IV→ III→ II
Explanation: The correct sequence for DNA fingerprinting using the Southern blot test is IV→ II→ III→ I. This process begins with digestion with restriction enzyme (IV), which cuts the DNA into fragments. Next, these fragments are separated by size using electrophoresis (II). The separated DNA fragments are then transferred to a membrane and hybridized with a radioactive probe (III) that binds to specific sequences. Finally, the pattern of the labeled fragments is visualized using X-ray film (I). Other options are incorrect as they do not follow this established sequence.
Correct answer: IV→ II→ III→ I5232. In the annealing (second) step of polymerase chain reactions (PCR), temperature is lowered to 55-65°C. The reason for lowering the temperature is to:
- A. Activate the Taq polymerase enzyme
- B. Extend the primers to synthesise new strands of DNA
- C. Make single-stranded DNA template for the next step
- D. Allow the binding of primers to their complementary sequences
Explanation: During the annealing step of PCR, the temperature is lowered to approximately 55-65°C to allow primers to bind or anneal to their complementary sequences on the single-stranded DNA. This is crucial for the next step where Taq polymerase extends the primers and synthesizes new DNA strands. Option D is correct as it describes this process. Option A is incorrect because Taq polymerase activation primarily occurs during the extension phase at around 72°C. Option B is incorrect because primer extension is not the purpose of the annealing step. Option C is incorrect as the formation of single-stranded templates occurs during the denaturation step, not annealing.
Correct answer: Allow the binding of primers to their complementary sequences5233. Sameen is 20 weeks pregnant. Her doctor came to know that she has a family history of Down's syndrome.The prenatal diagnostic test that the doctor would recommend her to check the presence of this disease in the baby is:
- A. X-ray
- B. Ultrasound
- C. Amniocentesis
- D. Complete Blood Count
Explanation: The correct answer is amniocentesis. This procedure involves extracting a small amount of amniotic fluid, which contains fetal cells, to analyze for chromosomal abnormalities such as Down's syndrome. While an ultrasound is used to visualize the fetus's physical development, it is not a diagnostic tool for chromosomal disorders. An X-ray is not suitable due to radiation exposure and its ineffectiveness in diagnosing such conditions. A complete blood count is unrelated to chromosomal testing and focuses on blood cell levels.
Correct answer: Amniocentesis5234. Specific sequences of four or six nucleotides arranged symmetrically in reverse order where restriction enzymes work are known as
- A. Okazaki fragment
- B. Palindromic sequences
- C. Promoter sequences
- D. Primer
Explanation: In molecular biology, palindromic sequences are referred to as the sequence of nucleotides in the DNA duplex or RNA, where the sequence in one strand is the same as the complementary sequence of the other strand when read from the same direction on both the strands, either 5' to 3' or 3' to 5'.
Correct answer: Palindromic sequences5235. During PCR which enzyme is used to do polymerization of DNA fragments
- A. RNA polymerase
- B. DNA polymerase
- C. Taq polymerase
- D. DNA ligase
Explanation: Like DNA replication in an organism, PCR requires a DNA polymerase enzyme that makes new strands of DNA, using existing strands as templates. The DNA polymerase typically used in PCR is called Taq polymerase, after the heat-tolerant bacterium from which it was isolated (Thermus aquaticus).
Correct answer: Taq polymerase5236. Study of proper utilization of economically important domesticated animal is known as
- A. Animal husbandry
- B. Wild life management
- C. Hybrid breeding
- D. Livestock management
Explanation: The study of the proper care, breeding, and management of economically important domesticated animals is known as animal husbandry. It involves various practices aimed at maximizing the productivity, health, and welfare of livestock such as cattle, sheep, poultry, and pigs, among others. Animal husbandry is crucial for ensuring efficient utilization of these animals for food, fiber, work, and other purposes.
Correct answer: Animal husbandry5237. The physical method used to control Bacteria is
- A. Antiseptics
- B. Disinfectants
- C. Pasteurization
- D. Antibiotics
Explanation: Pasteurization is indeed a physical method used to control bacteria in food and beverages. It involves heating the product to a specific temperature for a set period, effectively killing harmful bacteria and pathogens while preserving the taste and quality of the food or beverage.
Correct answer: Pasteurization5238. Which one of the following recombinant DNA technology tool is incorrectly paired with its use?
- A. Restriction endonuclease-production of RFLP
- B. DNA ligase-production of sticky ends in restriction fragments
- C. Reverse transcription-production of cDNA
- D. PCR-gene amplification
Explanation: PCR is a very sensitive technique that allows rapid amplification of a specific segment of DNA. PCR makes billions of copies of a specific DNA fragment or gene, which allows detection and identification of gene sequences using visual techniques based on size and charge.
Correct answer: PCR-gene amplification5239. A paleontologist has recovered a bit of tissue from 500 years old preserved skin of an extinct bird. The researcher would like to compare DNA from the sample with DNA from a living bird. Suggest the technique that would be more useful for increasing the amount of DNA available for testing.
- A. Gel electrophoresis
- B. RFLP analysis
- C. Polymerase chain reaction
- D. Tissue culture
Explanation: PCR is a technique used to amplify a specific region of DNA, generating millions of copies of that region. This is likely the most useful technique for increasing the amount of DNA available for testing in this scenario. With PCR, even minute amounts of DNA can be amplified to a level where they can be analyzed.
Correct answer: Polymerase chain reaction5240. Restriction endonucleases can be used in Genetic Engineering to
- A. Produce cDNA
- B. Cut plasmid DNA
- C. Join DNA at sticky ends
- D. Clone DNA
Explanation: In genetic engineering, restriction enzymes are used for cutting DNA fragments. A restriction enzyme (or restriction endonuclease) is an enzyme that cuts any DNA at or near specific recognition nucleotide sequences (known as restriction sites).
Correct answer: Cut plasmid DNA