Range of DNA variation in humans

[Darth Wong]

What is the known range of DNA variation in human beings? Does anyone know of a source for this data, ie- how many differences in DNA can you find between one person and another?

[Vendetta]

A quick google turned up this:

How Much Genetic Variation Exists Among Humans?

Homo sapiens is a relatively young species and has not had as much time to accumulate genetic variation as have the vast majority of species on earth, most of which predate humans by enormous expanses of time. Nonetheless, there is considerable genetic variation in our species. The human genome comprises about 3E9 base pairs of DNA, and the extent of human genetic variation is such that no two humans, save identical twins, ever have been or will be genetically identical. Between any two humans, the amount of genetic variation—biochemical individuality—is about 0.1 percent. This means that about one base pair out of every 1,000 will be different between any two individuals. Any two (diploid) people have about 6E6 base pairs that are different, an important reason for the development of automated procedures to analyze genetic variation.

So, about 0.1%.

Additionally, the likely variation between two individuals is greater between africans than everywhere else in the world put together.

[RedImperator]

I don't know the exact numbers, but I do know it's very low for mammals, especially one that's so widespread, and much of the variation that does exist is within Africa--only a small percentage of the existing human population at the time actually left Africa when Homo sapiens migrated out, and their descendants populated the entire rest of the world.

[The Nomad]

My first year molecule biology course says that the average heterozygoty is about 0.08% between two human individuals (about one difference for every 1,250 base pairs), which means that the global homology between the genome of two human beings is around 99.92%. It is about 96.50% between humans and chimpanzees, and 80% between humans and mice.

[Fire Fly]

Additional sources: Link

How different is one human genome from another?

The more closely related two people are, the more similar their genomes. Scientists estimate that the genomes of non-related people—any two people plucked at random off the street—differ at about 1 in every 1,200 to 1,500 DNA bases, or "letters." Whether that's a little or a lot of variation depends on your perspective. There are more than three million differences between your genome and anyone else's. On the other hand, we are all 99.9 percent the same, DNA-wise. (By contrast, we are only about 99 percent the same as our closest relatives, chimpanzees.)

Most genome variations are relatively small and simple, involving only a few bases—an A substituted for a T here, a G left out there, a short sequence such as CT added somewhere else, for example. Your genome probably doesn't contain long stretches of DNA that someone else's lacks.

If the genome were a book, every person's book would contain the same paragraphs and chapters, arranged in the same order. Each book would tell more or less the same story. But my book might contain a typo on page 303 that yours lacks, and your book might use a British spelling on page 135—"colour"—where mine uses the American spelling—"color."

As said before, the variation is about a 0.1% difference.

[kc8tbe]

It's hard to actually measure DNA variation because we don't (yet) have the technology to sequence entire individual genomes quickly enough.

For example, the figures you've probably read in your biology textbooks comparing humans to chimpanzees, gorillas, horses, dogs, and mice, are based on an cDNA analysis of hemoglobin alone.

We don't (quite) have a good figure for how similar the entire human genome is to that of a chimpanzee. And if we did, how useful would it be? Less important genes evolve faster then more important genes. A gene critical to reproduction evolves slowly, whereas a non-coding regions of DNA evolve very quickly. The rate of evolution is proportional to mutation rate and inversely proportional to selection pressure.

To answer your question: DNA sequence varies enough between individual humans that tandem repeats (non-coding regions) are a useful identifier in a criminal investigation. One in several million humans has the same sequence at a particular tandem repeat. But keep in mind that such non-coding regions have no phenotype.

The majority of the human genome is non-coding.

There are a bit over 25 human blood antigen types, although most people have one of 6 different types. Humans are considerably more diverse when it comes to the major histocompatability complex, otherwise it would be easier to get organ donations.

Perhaps a better question to ask is "How inbred are humans?" I don't remember the exact citation (I can find it if you really want to know), but humans were just below the gray wolf in degree of inbreeding and above most other animals at around 75% (compare to a mean of 40%).

[The Nomad]

I might add that the 0.08% difference is between two unrelated humans.