Cytogenetic and Allied Studies in Populations Exposed to Radiations and Chemical Agents
Genetic hazards to man following exposure to environmental mutagens are in many people’s minds associated with mutational changes induced in germ cells and then transmitted to offspring. These mutations, whether spontaneous or induced, can be broadly classified into one of two categories: (a) chromosomal mutations, which involve either a change in the structure or a change in the number of chromosomes and which are changes that can be readily visualised in chromosome preparations analysed under the microscope, and (b) gene mutations, which encompass a range of changes from single base pair substitutions in DNA to frame shifts involving single base or much larger deletions and including also the loss of very much larger DNA segments encompassing one or more genes from a given chromosome region. There is considerable overlap between these two categories of chromosomal and gene mutations and it is quite evident that many things that we see inherited as single phenotypic changes, that is apparently single gene effects — for example some of the thalassaemias — are really a mixed bag and may encompass quite large deletions which can sometimes be visualised under the microscope.
KeywordsGerm Cell Ankylose Spondylitis Somatic Mutation Chromosome Aberration Single Gene Mutation
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