//M0//QN1//CS//DL0

Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads variation in DNA. One DNA helix runs continuously from one end to the other in each chromatid, in a highly supercoiled form. Therefore loss (deletions) or gain (insertion/duplication) of a segment of DNA, result in alteration in chromosomes. Since genes are known to be located on chromosomes, alteration in chromosomes results in abnormalities or aberrations. Chromosomal aberrations are commonly observed in cancer cells.
(i) What is another phenomenon responsible for variation other than recombination? (a) Translation (b) Transcription (c) Mutation (d) Replication(ii) What kind of changes are occured as a result of mutation ? (a) genotype (b) phenotype (c) genotype and phenotype both (d) Behaviour of organism(iii) What are the reasons for alternation in chromosomes ? (a) Deletion of DNA segment (gene) (b) Insertion or duplication of DNA segment (gene) (c) A and B both (d) Unwinding of DNA helix only(iv) Where chromosomal aberrations are seen generally ? (a) Leucocytes (b) cancer cells (c) Erythrocytes (d) Normal skin cell

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