Tuesday, March 24, 2009


So for friends and family that hear what I do (Bioinformatics and Genomics) and automatically tune out - here is a short introduction - I'll add more later:

I study changes on the sex chromosomes (X and Y in mammals) and the autosomes (non-sex chromosomes). All humans have two copies of each of the 22 autosomes. In addition males have one X and one Y, whereas females have two X chromosomes. Below is a picture of the chromosomes from a human male:

The X and Y chromosomes used to be identical, but as you can see from the picture above, they are now very different in size, the X has about 2,000 genes, while the Y has fewer than 100. Many features are different between the X, Y and autosomes including the rate of nucleotide substitution.

More about nucleotide substitution:
There are 4 nucleotides, A, T, G, and C, that make up a DNA sequence and a substitution occurs when on base is substituted for another. For example, for two species, if one sequence is AAAG, and the second sequence is AAAT:

Human: A A A G
Chimp: A A A T

then we can infer that either there was a substitution from G -> T or from T ->G. By using a third species, called an outgroup, we can determine what is the most likely case:

Human: A A A G
Chimp: A A A T
Mouse: A A A T

Because the Mouse sequence also has a T, it is most likely that there was a change in the Human sequence from T -> G.

So, one of my research interests is to study how many substitutions there are on the X, Y and autosomes, across all nucleotides in the human genome (about 3 billion), how they differ, and why. That is where the Bioinformatics comes in.
Bio (for biology) and informatics (for large amounts of information). So, I study biology using lots and lots of information, more than was available even 10 years ago.

Next week's lesson: Genomics. :)

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