We'll have the code of three billion DNA letters in hand.

In principle, all people should have the same string of DNA letters in their mitochondria.

About 5,000 DNA letters degenerate per day in every human cell, and are immediately replaced by repair mechanisms.

There is only one problem: there is no sequence of DNA letters that encode for amino acids that nature has not encountered before.

The longest piece of inserted material so far is 2,000 DNA letters in length.

The machine cannot read individual DNA letters but rather markers attached to the DNA.

The variant forms have mutations, or changes of a single DNA letter, in the region of the gene assigned to the switching function.

It catalogs the patterns of small-scale variations in the genome that involve single DNA letters, or bases.

They show that large parts of the genome consist of duplications, with the identical sequence of DNA letters appearing twice over.

At issue are differences in a single DNA letter between one person and another.