Question

Why gene mutation cause different phenotypes in different individual?

Answer 1

So, how does a scientist relate differences in penetrance and expressivity that are observed at the phenotypic level to changes at the molecular level? For example, how is it possible that one family member carrying a retinoblastoma mutation has the disease, while another carrying the same mutation does not? What accounts for such a difference in disease penetrance? In the case of neurofibromatosis, family members carrying the same mutated neurofibromin gene are unequally affected by the condition, with some family members showing more severe symptoms than others. Why does this disease show variable expressivity? Answering these questions is not an easy task. Nonetheless, research has shown that variable phenotypes can be caused by a number of factors, including the following:

Modifier genes

Environmental factors

Allelic variation

Complex genetic and environmental interactions

In most cases in which a particular genotype is inherited, it is not fully known why the same allele can cause subtly different or profoundly different phenotypes. In some cases, however, there is genetic evidence that modifier genes influence phenotypic variation.

Modifier genes can affect penetrance, dominance, and expressivity. A genetic modifier, when expressed, is able to alter the expression of another gene. Modifier genes can affect transcription and alter the immediate gene transcript expression, or they can affect phenotypes at other levels of organization by altering phenotypes at the cellular or organismal level (Nadeau, 200