“SPONTANEOUS AND INDUCED MUTATION : UNRAVELLING MOLECULAR MECHANISM SHAPING GENETIC VARIATION”

UNIVERSITY OF AGRICULTURAL SCIENCES, BANGALORE

DEPARTMENT OF GENETICS AND PLANT BREEDING

M.Sc. Seminar - GPB 581 (0+1)

“SPONTANEOUS AND INDUCED MUTATION : UNRAVELLING MOLECULAR MECHANISM SHAPING GENETIC VARIATION”

Mutation is a stochastic yet heritable perturbation in the nucleotide sequence of an organism’s genome, underpinning molecular evolution, phenotypic variability, and pathophysiological manifestations. These alterations arise via endogenous biochemical mechanisms or through exogenous genotoxic insults, categorized as spontaneous mutations, which emanate from intrinsic cellular dynamics, and induced mutations, precipitated by mutagenic agents that disrupt genomic integrity. The interplay of mutational events with DNA repair mechanisms, epigenetic regulatory networks, and cellular stress responses dictates genome plasticity and organismal adaptability.

The physical mutagens in plants comprise non-ionizing or ionizing radiation, frequently causes double-strand DNA breaks and produces large deletion in DNA which leads to visual effects on the chromosome structure.¹ Gamma rays is used as physical mutagen in rice due to its convenience as well as its capability of penetrating deeper in the tissues. It induces nucleotide substitutions and small deletions of 2–16 bp, in addition mutation frequency is expected to be one mutation per 6.2 Mb. Furthermore, laser beams were demonstrated that are able to induce chromosome mutation.²

Chemical mutagens such as alkylating agents, base analogues, acridine dyes and deaminating agents are substances that induce mutations by altering the DNA structure, leading to genetic modifications. These mutagens can cause point mutations, insertions, deletions, and chromosomal aberrations, affecting gene function and cellular processes.¹

Mutation can be seen as a powerful strategy for direct release of improved varieties. Regarding bread wheat, 237 mutant varieties were released, out of which 195 were developed using physical mutagens, 40 using chemical mutagens and 2 varieties using their combinations.³ As mutation breeding is considered as a forward genetic approach, which produces novel phenotypes that can be exploited in classical breeding programs, which helps in deciphering the mechanistic underpinnings of mutagenesis is pivotal for advancing molecular genetics, and evolutionary biology.

REFERENCES:
1 KODYM, A. AND AFZA, R., 2003, Physical and chemical mutagenesis. Plant funct.Genom., 236:189-203.
2 RYOUHEI, M., MAKOTO, K., SHUICHI, L., HIROYASU, Y., TAKESHI, N. AND MINORU, N., 2019, Molecular characterization of mutations induced by gamma irradiation in rice. Genes Genet.Syst., 84:361-370.
3 GHADA, M.SH.M., ABAZA., HASSAN, A., AWAAD., ZAKARIA, M., ATTIA., KHALID, S., ABDEL-LATEIF., MOHAMED, A., GOMAA., SAFY, M.SH.M., ABAZA. AND ELSAYED, M., 2020, Inducing Potential Mutants in Bread Wheat Using Different Doses of Certain Physical and Chemical Mutagens. Plant Breed. Biotech., 8(3):253–264.