Interested in both genetics and Maury 😂 so please ELI5
In: Biology
A baby gets half their DNA from each parent which means that half of the DNA will almost exactly match each parent.
Paternity tests take advantage of the fact that a baby takes 50% of their DNA from their mother, and 50% from their father. So if you can look at the baby’s DNA compared to the actual dad’s, there will be a lot of DNA that’s shared between the two of them, while if you compare the baby’s DNA to a stranger’s (whoever’s not the father), it’ll have far less similarity. After all, we share 50% of DNA with our parents and siblings (on average), 25% with a half sibling, 12.5% with a first cousin, and so it’s very unlikely that we’ll share a lot of those DNA markers with a total stranger.
The most common method that’s used today involves a procedure that fragments the DNA and stretches it out into bands in a special gel. You can look at the samples from the baby and from the potential fathers and see where there are more similarities. The father and the baby won’t match on every single marker, because the baby only inherited half of the father’s DNA, but they’ll still match on many more points than between a third party.
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