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Chapter-26 Control of Gene Expression

BOOK TITLE: Textbook of Biochemistry for Dental Students

Author
1. Vasudevan DM
2. S Sreekumari
3. Vaidyanathan Kannan
ISBN
9789350254882
DOI
10.5005/jp/books/11333_26
Edition
2/e
Publishing Year
2011
Pages
5
Author Affiliations
1. Faculty of Medicine, Amrita Vishwa Vidyapeetham, (Amrita University), Kochi, Kerala, Formerly Principal, College of Medicine, Amrita, Kerala; Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, Amrita Vishwa Vidyapeetham (Deemed University), Cochin, Kerala, E-mail: dmvasudevan@aims.amrita.edu, PG Programs and Research College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India, College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India; Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, India
2. Jubilee Mission Medical College, Trissur, Kerala, Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India, Government Medical College, Thrissur and Thiruvananthapuram, Kerala, India; Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India; Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
3. Amrita Institute of Medical Sciences, Kochi, Kerala, India, Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, India, Believers Church Medical College and Hospital, Thiruvalla, Kerala, India
Chapter keywords

Abstract

An alteration in the genetic material results in a mutation. Mutation may be: (1) point mutation or (2) affecting large areas of the chromosome. Point mutation may be subclassified as: (a) substitution, (b) deletion, and (c) insertion. Effects of mutation may be: (1) silent, (2) missense but acceptable mutation, (3) missense but partially acceptable mutation, (4) missense but unacceptable mutation, (5) non-sense or terminator codon mutation, and (6) frameshift mutation. Manifestations of mutations may be: (1) lethal mutations, (2) silent mutations, (3) beneficial mutations, and (4) carcinogenic mutations. Any agent which will increase cell proliferation can cause increased rate of mutation; such substances are called mutagens. Most mutagens are carcinogens. Cell cycle is divided into G1, G2, S and M phases. Induction is the phenomenon of increased synthesis of protein or enzyme in response to certain signal. Operon is a unit of gene expression; it includes structural genes, control elements, regulator or inhibitor gene, promoter and operator areas. When lactose is available in the surroundings, lac operon is derepressed; lactose is the inducer of lactose utilizing enzyme. Repression is the mechanism by which the excess product of a pathway shuts off the synthesis of the key enzyme of that pathway; ALA synthase is repressed by heme.

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