Principles of Microbiology

Principles of Microbiology Summary:

Swastik Publishers | 2009 | ISBN: 8189981277, 9788189981273 | 301 pages | PDF | 13,7 MB

Introduction

Genetic determinants have been shown to consist of deoxyribonucleic

acid (DNA) and ribonucleic acid (RNA). Enzymes are synthesized

under the direction of nucleic acids, and enzymes, thus synthesized,

are responsible for essentially all processes that occur in

microorganisms. Experiments with. both bacteria (pneumococci) and

viruses (radioisotope tests) have established roles of nucleic acids as

determinants in microbial variations.

Microorganisms are excellent for genetic studies, primarily because

of haploid conditions in many of them and the ability of observers to

detect mutations easily and test very large populations in short time

periods. Permanent changes in bacteria can be differentiated from

induced temporary types by fluctuation and replica plate techniques.

Changes in DNA structure are termed mutations, and they occur in

genes of chromosomes. Each gene may have a multiplicity of mutable

sites. Since codons code for amino acids, a missense mutation occurs

when a codon that codes for a new amino acid replaces a codon of

a DNA chain, and a nonsense mutation results from replacement with

a codon that codes for no amino acid. An altered nucleotide sequence

may be restored to its original order by a reverse mutation, or an

altered nucleotide sequence may be compensated for through a

suppressor mutation. Either the DNA structure or the manner in which

RNA is read may be altered.

Download

or
Download