Do organisms that have identical DNA always share a common p

Do organisms that have identical DNA always share a common phenotype (think of identical twins)? What can account for observed differerences in phenotype?

Solution

The two main functions of gene is to encode protein, it is either structural protein (muscle, microtubule, hair protein etc) or proteins which catalyze the chemical reactions of the cell.

So genes determine both biological structure and functions. Organisms with identical DNA will not always share a common phenotype. In case of monozygotic twins, two babies will get identical genes as single fertilized egg will divide to produce them, will resemble each other physically. But it has been observed if these twins are grown in two different environments, differences will come up in them due to the effect of environment. This clearly proves the role of environment on influencing the gene action.

Epigenetic mechanism was held responsible for the differences in physical appearance in the absence of observable environmental differences. Thus it has clearly proved in many studies that the environmental differences will increase the degree of phenotypic variation.

As a conclusion we can say, two genetically identical individual in different environments will develop differently, but the genetically different individuals in the same environment will develop differently.

This clearly states that only genetic similarity alone is not enough to get similar kind of phenotype, but in addition to that similar environment is also needed for have similar kind of phenotype.

Different environments will results in variations in phenotypes.

An identical twin that has got identical genetic material is seen expressing different physical and mental characteristics if they are allowed to grow up in different environments.