Raising a large number of identical plants from a small piece of tissue in a nutrient medium is called
- A.Micropropagation
- B.Hybridisation
- C.Grafting
- D.Vernalisation
Correct answer
Explanation
The correct answer is A, micropropagation. A small piece of tissue called an explant is placed in a sterile nutrient medium with growth regulators, it forms an unorganised mass called a callus and then whole plantlets, because a plant cell is totipotent, that is, able to give rise to a complete plant; the plants so raised are genetically identical and are called somaclones, and the method is used for banana, sugarcane and orchids, while meristem culture gives virus free stock. Option B, hybridisation, is the crossing of two different parents to combine their characters and gives plants that are not identical. Option C, grafting, joins a shoot of one plant to the root of another and is an old horticultural practice, not a laboratory one. Option D, vernalisation, is the need of some plants for a cold period before flowering.
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Practice Questions
View allWhich enzyme cuts DNA at a specific recognition sequence and is therefore called molecular scissors?
- A.DNA ligase
- B.Restriction endonuclease
- C.DNA polymerase
- D.Reverse transcriptase
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A restriction endonuclease recognises a short palindromic sequence in DNA and cuts both strands there, leaving sticky ends that can pair with another piece cut by the same enzyme; Hind II was the first such enzyme to be discovered and EcoRI from Escherichia coli is the most widely used.
Read the full explanation →Which bacterium is used as a natural vector to transfer genes into plant cells?
- A.Escherichia coli
- B.Agrobacterium tumefaciens
- C.Bacillus thuringiensis
- D.Rhizobium leguminosarum
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This soil bacterium naturally transfers a part of its tumour inducing plasmid, called the Ti plasmid, into the cells of a dicotyledonous plant and causes crown gall disease; genetic engineers disarm the plasmid, insert the gene they want and use the bacterium as a vector, which is why it is…
Read the full explanation →The insect resistance gene of Bt cotton is obtained from which organism?
- A.A virus
- B.A soil bacterium
- C.A fungus
- D.An alga
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The genes called cry genes are taken from Bacillus thuringiensis, a bacterium of the soil that forms protein crystals during its spore stage.
Read the full explanation →Golden Rice is a genetically modified variety enriched with which substance?
- A.Iron
- B.Beta carotene
- C.Lysine
- D.Vitamin C
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Golden Rice carries genes that let the grain make beta carotene, the orange pigment that the human body converts into vitamin A, and the colour of the grain gives the variety its name; the aim is to reduce night blindness and childhood blindness in populations whose diet is mainly rice.
Read the full explanation →Which heat stable enzyme is used in the polymerase chain reaction?
- A.Taq polymerase
- B.DNA ligase
- C.EcoRI
- D.Lysozyme
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The polymerase chain reaction repeats three steps, denaturation at a high temperature, annealing of short primers and extension of the new strand, so the enzyme must survive near boiling water; Taq polymerase, obtained from the bacterium Thermus aquaticus of hot springs, does exactly that and lets a single DNA segment…
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