bethanym1998 to Anna, Jane, Iain, Nick on 19 Mar 2014.
Nick Goldman answered on 19 Mar 2014:
Everyone’s DNA is different because everyone gets a random mix of the genes from their mother and father, and that random mix is never the same.
Even identical twins have tiny differences in their DNA, because during our development and lifetime we all get a few tiny mutations and those are different in different people.
Anna Middleton answered on 19 Mar 2014:
Everyones’s DNA is basically the same in that we all have genes that give us eye colour and tell us to grow to a certain height etc. But individual genes are subtly different between people in that our eye colour is different and we are all slightly different heights. The variation between people is what makes us individuals and it is this variation that a lot of scientists around the world are exploring at the moment.
Jane Charlesworth answered on 19 Mar 2014:
First, not everyone has different DNA! Identical twins actually have exactly the same DNA as each other, at least when they are born.
For everyone else, though, we get half our DNA from each of our parents, in a random combination. In addition, when our bodies make the egg and sperm cells (each of which contain only half the DNA of our other body cells) the DNA can be mixed up when the cells divide, or small errors, called mutations can be introduced when the DNA is copied from the old cell to the new.
On average each person picks up one or two new mutations compared with their parents, but this can vary–older parents, for example are more likely to pass on more mutations to their kids. It is also possible for our body cells to get mutations as they divide, but those aren’t passed on to the next generation. This happens even to identical twins–so one twin could get cancer and the other one might be fine.
Iain Moal answered on 19 Mar 2014:
Everybody does have slightly different DNA, but the first thing to notice is how remarkably similar the DNA is between people. In fact, people share around 99.9% of our DNA with everyone else. However, because we have such a large amount of DNA, that 0.01% difference is actually quite a lot, and Nick and Anna have explained really well why we have those differences.
One interesting thing about differences in DNA is that in Africa there is more difference in DNA between people than in other places in the world. This is because humans evolved in Africa, and later migrated and colonised other parts of the world. Human settlements outside of Africa were founded by relatively small groups of travellers, and so have less variation in their DNA compared to people in Africa. In fact, you can use the information in your DNA to find out what route your ancestors took when they migrated out of Africa, and there are companies which can do this for you. I think this is really cool!