Four Types of Genetic Variation

We all have variants of the same 20,000 genes.  A recent article lists four types of genetic variations:

1) Single "letter" variations (called SNPs -- these often get inherited together in blocks called haplotypes), 2) additions or deletions (InDels) of DNA units, 3) repetitions like those that underlie forensic DNA tests, and 4) flipping of large segments of DNA within a chromosome.

Some things to keep in mind, however.  At the level of philosophy, it's more important to express the gene variation in terms of how much information is being stored in the genes, and how many different branching points and scenarios can be represented.  The physical manifestation of variation in the DNA is somewhat irrelevant, as long as the information is there.

For example, we each have a number of repeating units (of 48 or 120 DNA letters, or bases) in our DRD4 gene, which may be responsible for novelty-seeking behavior.  The number of repeats (3, 5, 7... etc) seems to encode the amount of risk-taking you are comfortable with.