All Free Biology MCQs with Answers
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19844 questions · page 528 of 1985
5271. So far 400 such enzymes have been isolated out of which about 20 are frequently used in recombinant DNA technology:
- A. Reverse transcriptase
- B. Helicases
- C. Ligase
- D. Restriction endonucleases
Explanation: A restriction enzyme, restriction endonuclease, REase, ENase or restrictase enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites.
Correct answer: Restriction endonucleases5272. Plasmids were discovered by the investigators studying the sex-life of the _ bacterium Escherichia coli.
- A. Faecal
- B. Intestinal
- C. Milk
- D. Soil
Explanation: Escherichia coli is predominantly found in the intestines of humans animals, which is why it is referred to as an intestinal bacterium.
Correct answer: Intestinal5273. Complementary DNA is synthesized by?
- A. DNA polymerases
- B. DNA ligases
- C. Restriction endonucleases
- D. Reverse transcriptases
Explanation: In molecular biology, complementary DNA (cDNA) is synthesised from an RNA template in a reaction catalysed by the enzyme reverse transcriptase (RTase). cDNA synthesis is the first step in many molecular biology workflows, such as gene expression studies using real-time PCR.
Correct answer: Reverse transcriptases5274. Bacteria produce a variety of restriction enzymes, which cut the DNA at specific sites, characterized by specific sequence of DNA arranged?
- A. Symmetrically in reverse order
- B. Asymmetrically in reverse order
- C. Symmetrically in same order
- D. Asymmetrically in same order
Explanation: Bacteria produce a variety of restriction enzymes, which cut the DNA at specific sites, charactanzed by specific sequance of DNA arranged symmatrically in reverse order.
Correct answer: Symmetrically in reverse order5275. Which one produces androgenic haploids in anther cultures?
- A. Anther wall
- B. Tapetal layer of anther wall
- C. Connective tissue
- D. Young pollen grains
Explanation: Young pollen grains produced androgenic haploids in anther cultures while anther wall, tapetal layer of anther wall and connective tissue are the parts of anther.
Correct answer: Young pollen grains5276. A DNA molecule synthesized from mRNA by reverse transcriptase in laboratory is called?
- A. cDNA
- B. Extra chromosomal DNA
- C. Chromosomal DNA
- D. Cytoplasmic DNA
Explanation: cDNA (short for copy DNA, also called complementary DNA) is synthetic DNA that has been transcribed from a specific mRNA through a reaction using the enzyme reverse transcriptase.
Correct answer: cDNA5277. Haploid plants can be obtained by culturing:
- A. Pollen grain
- B. Root tips
- C. Young leaves
- D. Endosperm
Explanation: Anther culture is done for production of haploids because anthers contain hapicid microspores (pollen grains) which can be used to generate new plants.
Correct answer: Pollen grain5278. Cellular totipotency was demonstrated by:
- A. Theodore Schwann
- B. A.V. Leeuwenhoek
- C. F.C. Steward
- D. Robert Hooke
Explanation: Professor F.C. Steward made significant contributions to the field of plant tissue culture. In 1958, he demonstrated calular totipotency by regenerating a whole plant from a single carrot cell, which established the potential for cells to develop into completa organisms.
Correct answer: F.C. Steward5279. What is the commercial method of producing millions of seedlings in limited time?
- A. Parthenogenesis
- B. Parthenocarpy
- C. Micropropagation
- D. Grafting
Explanation: Micropropagation is a tissue culture technique used commercially to produce millions of identical seedlings in a short time under controlled conditions.
Correct answer: Micropropagation5280. The ordered list of loci known for a particular genome is called?
- A. Gene map
- B. Loci
- C. Alleles
- D. Chromosomes
Explanation: A gene map shows the relative positions of genes (loci) on a chromosome.
Correct answer: Gene map