[texthompson]

> Someone probably told me that every cell in my body has the same DNA. But no one shook me by the shoulders, saying how crazy that was.

This is only mostly right. Every cell in your body has an astonishingly similar amount of DNA, but every cell division (and even steady state DNA repair) offers the opportunity for mutations. So your cells are all astonishingly similar, but there can be detectable differences.

One implication of this is that cells that are closer to each other in developmental history will have more similar DNA. One of my colleagues in graduate school used this to do phylogenetic lineaging, where he looked at markers in DNA from whole organisms to reason about which cells are closely related, and which cells have a more distant developmental ancestor.

Biology is super cool! I hope that everyone finds a little bit of it that they can enjoy. :)

[j7ake]

Also B cells and T cells undergo genomic rearrangements to get a diversity of receptors that can make specific targets.