I made an answer on the Scifi.SE that can be read here. It is about how the char

Question

I made an answer on the Scifi.SE that can be read here. It is about how the characters in the story Jurassic Park might have gotten DNA for all the species shown.

In my answer, I said this:

Apes and Humans, for example, share over 99% of their genes. That means the difference between our species is less than 1% of our genes. In fact, all life on Earth shares about 50% of it's genes.

but in the original posting (before someone edited it) I chose to use the word DNA instead of genes.

He left this comment in the section to explain the edit:

Sorry, I'm a biologist, I can't help it. Humans and apes share 99% similarity in the coding sequences of their DNA, the ~5% that codes for genes, not on all the DNA. I simplified this to genes for the answer.

I have a basic high school understanding of DNA and genes, so I'm afraid I fail to see the difference between using "DNA" or using "genes" in my statement. I understand that genes are specific sequences of DNA that are used by the cell in some way. I understand that DNA is more generic, including all of the strands, whether they are used or not, whether they seem to code for something or not.

So is it wrong then to say that apes and humans share 99% of their DNA or is it equally correct to say "genes"?

Explanation / Answer

So, a quick biology lesson, going backwards. Proteins are the things that make up a good percentage of our cells (which make up a good percentage of us), and are the things that do the work of the cells - many are also known as "enzymes". Proteins are encoded by genes - while the saying that one gene codes for one protein is now known to be pretty inaccurate (one gene can code for many different variations of the same basic protein), it's a good way to think about things in this context. Genes are made up of DNA, the "genetic code" that we hear about - the 4 billion (-ish) "letters" that make us who we are. However, now we get to the key part - all genes are made of DNA, but not all DNA is in a gene. In fact, as terdon mentioned in your comment, only about 5% (or less) of those 4 billion letters are in the expressed region of genes - those sequences that directly code for protein. The rest is regulatory, structural, and ... we're not exactly sure. Some call it "junk DNA", but it's stuck around for millions of years, so it must have some purpose, we just haven't figured it out yet. There are a lot of divergent sequences in this "non-coding" DNA between species, so it must somehow contribute to the differences between us, but how exactly that happens hasn't been elucidated yet.

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