Asked by newlearner1 | 27th Nov, 2009, 08:39: PM

Expert Answer:

These are germinal variations that occur in the genes of the organism and are hereditary in nature.

These changes may be due to any of the following:

i) Different combinations of genes during meiosis in sexual reproduction. An example of change due to meiosis is the difference in height of a population.

ii) Some sudden change in the composition of genes. An example of change in the gene structure is sickle-celled anaemia. In this, one of the genes undergoes a change in its composition. This results in the red blood cells being sickle shaped.

iii) Change in chromosome number.  An example of this is Down's syndrome wherein the individual has an extra 21st chromosome. Hence the person is mentally retarded, has moon face, thick lips and generally does not live upto the reproductive age.

Answered by  | 2nd Dec, 2009, 09:23: AM

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