Effects of Mutations
The effect of mutation is dependent on the scale of change.
If mutation occurs in somatic cells, only dominant mutation genes can be shown. Then, the feature and effect can be observed. If the mutation gene is recessive, nothing can be observed or detected.
Somatic mutation can just affect the cell itself, or its derivatives. Therefore, it is restricted and cannot affect the offspring. If the mutation cells die off or is replaced, the mutation gene would disappear also.
If mutation occur in germinal cells, the effect would be different.
If mutation occurs in a sperm or an egg, the mutation would disappear as they do not fertilize. If the mutation sperm or egg is fertilized successfully, the mutation gene would be brought to the next generation.
If mutation occurs in sperm mother cell or egg mother cell, all gametes derived from them would carry the mutation gene. Therefore, the mutation gene produced in germ mother cells would have a greater chance of survival than those occurred in individual somatic cells.
Most survived mutation genes are recessive, because most mutation genes have the lethal effect. Once it is dominant, the individual would be dead, even though it is heterozygous. If the mutation gene is recessive, they can be shielded by the normal dominant gene. So, they can exist and can be brought to the next generation. But, to observe the effect of a recessive mutation gene is difficult, because all individuals are diploid. When it exist solely, it is a gamete and will not show any trait. If it is not a human, then, we can use back-cross to cultivate the homozygote and observe the expression of the mutation gene. But if it is a human, then, nothing can be done.
(23.05.2007)
