Why is it virtually impossible for two people who aren't twins to have the same DNA?

Answer 1

Human DNA is very complex with a very large number of genes and a lot of diversity in certain genes. Therefore, when DNA is mixed from two individuals it is virtually impossible for the mixture to be the same every time in the small number of offspring produced in the lifetime of humans. Further, there are two reproductive factors that make it statistically improbable to have the exact same DNA passed on to two individuals.

First, there is a low occurrence of generational inbreeding in humans, which could increase the chances of two individuals sharing the same DNA as is done in lab animals such as mice and rats.

Second, the process of meiosis, which is the production of sex cells in an individual, includes complex mechanisms to guarantee genetic diversity. Every cell in your body has two copies of DNA from each parent except meiotic cells (sex cells), which only contain one set of DNA. This single set of DNA is a mix of genes from both sets of an individual's parents. The mix is somewhat random, thus the genes passed on from two parents are highly unlikely to be the same on any two given conceptions.<br>

Answer 2

Each person's DNA is a unique combination of genes inherited from their parents, contributing to the vast genetic diversity in the population. The probability of two unrelated individuals having the exact same DNA sequence is extremely low due to the large number of possible gene combinations and genetic variations that exist in the human genome.