why do all cells in a body have to have a copy of the whole DNA?

Question

For example why does a skin cell has a copy of how to make blood cells if their only job is just to do skin cell things?

In: Biology

Answer 1

Life isn’t “developed” like a computer program which has different parts for different applications. What is responsible for what; and where these things are located on the genome is random. Everything is mixed up.

So you can’t just take all the skin cell things and separate them from the blood cell things, because in the best case it would mean cutting out and rearranging 1000s of tiny snippets. Moreover, the presence of DNA alone isn’t the whole picture. Skin and blood cells might use the same gene, but one uses it more actively, therefore its function is more pronounced. Or they use the same gene to make different protein via alternative splicing.