With the exception of identical twins it is said that no two

With the exception of identical twins, it is said that no two people are just alike. But is this true? Is it virtually impossible for people other than identical twins to have exactly the same DNA and be identical to each other? Why or why not? Please explain your answer!

Solution

See even though brothers have similar father and mother they too are not identical. The reason behind it is crossing over occuring in the meiosis forming a totally new blend ( combination chromosomes ) from parental chromosomes. This crossing over is a total random event and is the reason for all the variation occuring in the genome. In case of monozygotic identical twin what happens is after the cossing over, zygote is formed, this zygote divides by mitosis forming exact two identical cells which then act as independant zygotes and have totally similar GENETIC makeup.

In other case assuming that crossover happening in two different independantly developed zygotes from similar parents would be exactly the same counts for a very very very very nil nil nil infact not at all possibility. Hence no two different zygotes developed independantly even though from a single parents would be the same. except when zygotes divide byt mitosis in case of monozygotic twins.

So it is never possible to have IDENTICAL DNA between the two persons of different independantly zygotic orgin because of probability rules governing random crossover in meiosis .

Hope it helps, I TRIED TO MAKE IT SIMPLE AND MEANINGFUL FOR YOU , Feel free to comment and discuss .... Regards.