Before considering microsatellites in detail, let's look for a moment at DNA and the nucleotides that combine to form it.
There are four nucleotides that—when combined in long chains—make a DNA molecule. The four nucleotides are: adenine (A), thiamine (T), guanine (G), and cytosine (C). To depict a DNA molecule in shorthand form, scientists often use the abbreviations A,T,G, and C for each of the four nucleotides (adenine, thiamine, guanine, and cytosine, respectively) to describe the DNA sequence.
For example:
GTACCGAATGTCTG
But this only describes a single strand of DNA and DNA consists of two strands. Yet, knowing the one strand, we are able to figure out what its compliment should be because each nucleotide forms a base pair according to the following simple rule: adenine (A) only pairs with thiamine (T) and guanine (G) only pairs with cytosine (C).
So the sequence GTACCGAATGTCTG, when considered as a double strand of DNA, looks like this:
GTACCGAATGTCTG
CATGGCTTACAGAC
DNA strands are very long and, depending on the species, consist of potentially billions of base pairs. Scientists often focus on small segments of DNA during their study of an organism
In most instances, microsatellites consist of one, two, three, or four nucleotides.
