Everything you need to know about mutation breeding !
Q. 1. What is mutation?
Ans. Mutation refers to sudden heritable change in the phenotype of an individual. In molecular terms, mutation is defined as the permanent and relatively rare change in the number or sequence of nucleotide.
Q. 2. Who first discovered mutation?
Ans. Mutation was first discovered by Wright in 1791 in male lamb that had short legs.
Q. 3. Who first discovered mutation in plants?
Ans. In plants, mutation was first discovered in 1900 by de Vries in Oenothera.
Q. 4. Who coined the term mutation?
Ans. The term mutation was coined/first used by de Vries in 1901.
Q. 5. Who first discovered mutation in Drosophila?
Ans. In Drosophila, the white eyed mutatant was first discovered in 1910 by Morgan.
Q. 6. What are different types of mutation?
Ans. Mutations have been classified in various ways as follows:
Q. 7. What are macro-mutations?
Ans. Induced mutations are of two types, viz. macro-mutations and micro- mutations. Mutations with distinct morphological changes in the phenotype are called macro-mutations. Such mutations are found in qualitative character and, therefore, are also called oligogenic mutations. Identification of such mutations is easy.
Q. 8. Who coined the term macro-mutation?
Ans. The term macro-mutation was first used by Gold Schmidt in 1940.
Q. 9. What are micro-mutations?
Ans. Mutations with invisible phenotypic changes are called micro-mutations. Such mutations are observed in quantitative characters and, hence are also known as polygenic mutations. Identification of such mutations is very difficult. Micro-mutations are of economic value in plant breeding.
Q. 10. Define lethal mutation?
Ans. A mutation which kills all the individuals that carry it is called lethal mutation.
Q. 11. What is sub-lethal mutation?
Ans. A mutation which kills more than 50% of individuals that carry it is termed sub-lethal mutation.
Q. 12. Define sub-vital mutation.
Ans. A mutation which kills less than 50% of individuals that carry it is known as sub-vital mutation.
Q. 13. What is vital mutation?
Ans. A mutation in which all the mutants survive is called vital mutation.
Q. 14. What is point mutation?
Ans. Gene mutation or mutation at molecular level is called point mutation. The term point mutation was first used by Bridges in 1923.
Q. 15. What is mutagen?
Ans. Physical or chemical agents which greatly enhance the frequency of mutation are called mutagens.
Q. 16. What are physical mutations?
Ans. Physical mutagens include various types of radiations as given below:
(ii) Gamma rays
(iii) Alpha rays
(iv) Beta particles
(v) Fast neutrons
(vi) Thermal (slow) neutrons
(vii) Ultraviolet rays.
Q. 17. What are sparsely ionizing radiations?
Ans. Sparsely ionizing radiations include X-rays, Gamma rays and Beta particles.
Q. 18. What are densely ionizing radiations?
Ans. Fast and thermal neutrons and alpha particles are densely ionizing radiations.
Q. 19. Who discovered X-rays?
Ans. X-rays were first discovered by Roentgen in 1895.
Q. 20. Who first used X-rays for induction of mutation?
Ans. Muller first used X-rays for induction of mutation in 1927 in Drosophila.
Q. 21. Who first used X-rays for induction of mutation in crop plants?
Ans. Stadler in 1928 first used X-rays for induction of mutation in barley.
Q. 22. Who won Nobel Prize for induction of mutation?
Ans. Muller, a US genelicist, was awarded Nobel Prize in 1946 for experimental induction of mutation in Drosophila.
Q. 23. How X-rays induce mutations?
Ans. X-rays induce mutations by forming free radicals and ions. X-rays cause both chromosomal and gene mutations.
Q. 24. How gamma rays induce mutations?
Ans. Gamma rays induce chromosomal and gene mutations by ejecting atoms from the tissue.
Q. 25. How gamma rays are generated?
Ans. Gamma rays are generated from radioactive decay of some elements such as 14C, 60C, radium etc. The Cobalt-60 is commonly used for the production of gamma rays.
Q. 26. How alpha particles induce mutation?
Ans. Alpha particles induce chromosomal mutations through ionization and excitation.
Q. 27. How beta particles are generated?
Ans. Beta particles are generated from radioactive decay of heavier elements such as 3H, 32P, 35 S etc.
Q. 28. How ultraviolet rays are generated?
Ans. Ultraviolet rays are generated from mercury vapour lamps or tubes. They are also present in solar radiation. They are non-ionizing and low penetrating.
Q. 29. What are chemical mutagens?
Ans. There is a long list of chemicals which are used as mutagens.
Chemical mutagens are divided into following four groups:
(i) Alkylating agents
(ii) Base analogues
(iii) Acridine dyes
Q. 30. What are alkylating agents?
Ans. Chemical mutagens which cause mutation by adding alkyl group at various positions in DNA are called Alkylating agents. Such chemicals cause mutation through transitions.
Examples of alkylating agents are given below:
(i) Ethyl methane sulphonate
(ii) Methyl methane sulphonate
(iii) Ethyl ethane sulphonate
(iv) Ethylene imines.
Q. 31. What are base analogues?
Ans. Chemical compounds which are similar to DNA bases are called base, analogues. Base analogues include 5 Bromo Uracil and 2 Amino Purine.
Q. 32. What are acridine dyes?
Ans. Acridine dyes are very effective mutagens. They lead to addition or deletion and cause frame-shift mutations.
Acridine dyes which used for induction of mutation are given below:
Proflavin – Acriflavin
Acridine orange – Ethadium bromide
Acridine dyses are also known as frame-shift mutagens.
Q. 33. What are frame-shift mutations?
Ans. Mutations which arise due to addition or deletion of nucleotides in mRNA are called frame-shift mutations. Such mutations are induced by acridine dyes.
Q. 34. Who first used the term frame-shift mutation?
Ans. The term frame-shift mutation was first used by Brenner et al. in 1961.
Q. 35. Define transition.
Ans. Substitution of one purine by another purine or one pyrimidine by another pyrimidine is called transition. The term transition was coined by Freese in 1959.
Q. 36. What is transversion?
Ans. Substitution of a purine by a pyrimidine or vice-versa is known as transversion. The term transversion was coined by Freese in 1959.
Q. 37. What are nonsense mutations?
Ans. Mutations which have nonsense codons are called nonsense mutations. The term nonsense mutation was coined by Brenner et al in 1961.
Q. 38. What are missense mutations?
Ans. Mutations which have missense codons are termed missense mutation. The term missense mutation was coined by Brenner et al. in 1961.
Q. 39. What is tautomerization?
Ans. The process of shifting hydrogen atoms from one position to another in a purine or pyramidine base in called tautomerization. The product of this process is known as tautomer.
Q. 40. What is mutator gene?
Ans. Gene which enhances the natural mutation rate of other genes in the same genome is called mutator gene. Example is dotted gene is maize. The term mutator gene was coined by Demerec in 1937.
Q. 41. What is mutable gene?
Ans. A gene which exhibit higher mutation rate than other genes is called mutable gene.
Q. 42. What is antimutator gene?
Ans. A gene which reduces the frequency of spontaneous mutation of other genes in the same genome is called anti-mutator gene. Such genes have been reported in bacteria and bacteriophages.
Q. 43. Who coined the term anti-mutator gene?
Ans. The term anti-mutator gene was first used by Drake and Allen in 1968.
Q. 44. What is mutation load?
Ans. Decrease in the relative fitness of a genotype due to presence of deleterious mutation is called mutation load. The term mutation load was coined by Muller in 1950.
Q. 45. What is mutation pressure?
Ans. Increase of a mutant allele in a population due to its recurrent production is called mutation pressure. The term mutation pressure was first used by Wright in 1921.
Q. 46. What is muton?
Ans. A subdivision of gene which is the site of mutation is called muton. The term muton was coined by Benzer in 1957.
Q. 47. What are hot spots?
Ans. Highly mutable sites within a gene are called hot spots. The term mutational hot spot was coined by Benzer in 1955.
Q. 48. What is LD 50?
Ans. A dose of mutagen that kills 50% of treated individuals is called LD 50.
Q. 49. Define mutability.
Ans. The property of any gene or genotype to undergo mutation is called mutability.
Q. 50. What is mutagenicity?
Ans. Any event that leads to alteration of DNA is called mutagenicity.
Q. 51. Who coined the term mutation repair?
Ans. The term mutation repair was first used by Helsings et al in 1976.
Q. 52. What is mutation breeding?
Ans. The genetic improvement of crop plants for various economic characters through the use of induced mutations is called mutation breeding. Mutation breeding is used when desired variability is not found in the germplasm of cultivated species.
Q. 53. What steps are involved in mutation breeding?
Ans. The process of mutation breeding consists of following important steps:
(i) Choice of plant material
(ii) Choice of mutagen
(iii) Mutagen treatment
(iv) Handling of treated material
(v) Identification of desired mutant
(vi) Evaluation of mutant.
Q. 54. What are main achievements of mutation breeding?
Ans. The main achievements of mutation breeding are given below:
(i) Development of improved varieties
(ii) Induction of male sterility
(iii) Production of haploids
(iv) Creation of genetic variability
(v) Overcoming self incompatibility
(vi) Improvement in adaptation.
Q. 55. What are limitations of induced mutations?
Ans. Main limitations of induced mutations are as follows:
(i) Most of the mutations are deleterious.
(ii) The frequency of desirable mutants is very low (0.1%).
(iii) Identification of polygenic mutations is difficult.
(iv) It requires screening of large populations.
Q. 56. Write the characters which have been improved through mutation breeding?
Ans. Mutation breeding has been used for improvement of various characters such as yield, quality, disease resistance, insect resistance, drought resistance, dwarfness, earliness, plant type and adaptation.
Q. 57. What are mutatant varieties of wheat?
Ans. Mutant varieties of wheat released in India include NP 836, JRC 7447, Pusa Lerma and Sharbati Sonora. However, now these varieties are not under cultivation.
Q. 58. List mutant varieties of rice released in India?
Ans. In rice several mutant varieties have been developed through X-rays, gamma rays and Ethyl methane sulphonate (EMS) as given below:
(i) X-rays – Biraj, CNM 20, LNM 25, CNM 31, CNM 6 and Jagannath.
(ii) Gamma rays – AU1, AU4, K84, Mohan, Padmini, Rasmi, Sattari, Hybrid mutant
(iii) EMS – PL 56, IIT 60, Indira and Prabhavati.
Q. 59. Name the mutant varieties of cotton released in India.
Ans. In cotton, some mutant varieties have been released through X-rays and Gamma rays as given below:
(i) X-rays: Indore 2, MA 9 and MCU 7
(ii) Gamma rays: MCU 10, Rasmi, DS 1 and Pusa Ageti.
Q. 60. What are mutant varieties of barley?
Ans. Mutant varieties of barley include DL 253 (gamma rays), PL 56 (EMS) and RDB (N).
Q. 61. What are mutant varieties of sugarcane?
Ans. The mutant varieties of sugarcane include Co 6608, Co 8153 and Co 997. All these varieties have been developed through gamma rays.
Q. 62. What are mutant varieties of chickpea?
Ans. Mutant varieties of chickpea released in India include Pusa 408, Pusa 413, Pusa 417 (gamma rays) and Kiran (TN).
Q. 63. What are mutant varieties of groundnut?
Ans. In ground nut, mutant varieties have been released through X-rays, Gamma rays and EMS as given below:
(i) X-rays – TG3, TG4, TG17 and Vikram
(ii) Gamma rays – BP1 and BP2
(iii) EMS – CO2
Q. 64. What are mutant varieties of cowpea?
Ans. The mutant varieties of cowpea include V16, V37, V38 and V240, all developed through chemical mutagen (dMS).
Q. 65. List mutant varieties of mung-bean.
Ans. In mung-bean some mutant varieties have been developed through gamma irradiation. These varieties are Co4, ML 26-10-3, Pant Mung 2 and TAP 7.
Q. 66. What are mutant varieties of pigeon-pea?
Ans. Important mutant varieties of pigeon-pea released in India are CO3 (EMS), TAT5, Trombay (FN) and Co6 (gamma rays).
Q. 67. What are mutant varieties of tomato?
Ans. Mutant varieties of tomato include PKM1, S 12 and Pusalal Meeruthi.
Q. 68. What is difference between mutant and segregant?
Ans. There are two main differences between mutant and segregant as follows:
(i) The frequency of mutant is very low, whereas the frequency of segregant is quite high.
(i) The mutant differs from parent variety in one or few characters, whereas the segregant will differ from the parent variety in several characters.
Q. 69. Give the names of organizations where mutation breeding work is carried out in India.
Ans. In India, mutation breeding work is carried out in the following organizations:
(i) Bhapba Atomic Research Centre, Trombay, Mumbai.
(ii) ICAR Crop Research Institutes
(iii) State Agricultural Universities, and
(iv) In some general universities.
Q. 70. Where is the IAEA located?
Ans. The International Atomic Energy Agency is located at Vienna, Austria.
Q. 71. Give the names of some renound mutation breeders.
Ans. Names of some renound mutation breeders are given below:
(i) H.J. Muller (USA)
(ii) L.J. Stadler (USA)
(iii) C. Aureback
(iv) Brock, R.D.
(v) AU Harten
(vi) M.S. Swaminathan
Q. 72. Compare hybridization method and mutation breeding.
Ans. Comparison of combination (hybridization) breeding and mutation breeding is presented below in Table 18.1: