There are a lot of threads and posts in this section that can be quite confusing to the average person reading them. So here is a primer on DNA facts.

Nucleotides are the alphabet of DNA. There are only 4 of them: Adenine(A), Thymine(T), Guanine(G), and Cytosine(C). They always go by pairs, A with T and G with C. Such pairs are called "base pairs".

The 46 chromosomes of human DNA are composed of 3 billion base pairs. The Y chromosome has 60 million base pairs. The X chromosome has 153 million base pairs. Mitochondrial DNA is found outside the cell's nucleus and therefore outside of the chromosomes. It consists of only 16,569 base pairs. MTDNA is only passed by the mother to her offspring.

A single nucleotide polymorphism(SNP) is a mutation in a single base pair. Only a few hundred SNPs define all the human haplogroups for Y DNA or MTDNA.

Only 2% of DNA codes for proteins that change a body. There are pieces of DNA called switches. They cause protein changes the make species different. By flipping switches you can end up with totally different structures, different kinds of hands, different size brains, all things that can make a different species.