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.
or
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