How do I write a good abstract?
One of the things that is too much overlooked is that an abstract is read by a more diverse crowd of people than the rest of your paper. So, you have three different goals:


Give a take-home message to people who aren't interested enough to read the full paper.
Convince the undecided to read it.
Make it easier for experts to find it.


Nowadays, #3 is not so much of a constraint: Google and other search engines allow for full-text searching. So, focus on #1 and #2: be concise, crystal-clear, attractive.



Enough with the generalities. I love to critique, so I'll give it a try: I'm not in your field, which I think makes me a good test reader for your abstract, but also makes it harder for me to actually suggest actual changes to it. Anyway…

I think it's decent: no catastrophe, but far from enthusiastic. My main comment would be that it lacks a clear statement of the broader issue you are trying to address. You could start with it, something like:


  The past few years have seen large advances in the statistical modeling of DNA sequences, mostly based on genetic algorithms. In this work, we explore the efficiency of an alternative and simpler route, and show how to efficiently choose within a class of distribution models.


I have filled in with semi-random keywords/buzzwords, just to give you a sense of how to achieve it. The idea is to put your findings in perspective:


Roughly, what subfield are you working in?
What is the main trend in this field?
How do you position your work with respect to this recent research?


Then trim down the rest of the text:


  We showcase a method to select a Bayesian model for a collection of DNA sequences, generated from a specifically chosen distribution model capture long range correlation structure. We choose the model based its prior predictive distribution. Applying this method to model human and mouse Recombination Signal Sequences (RSS), we predict which of a larger group of sequences are RSS in the context of a cross-validation setup.


(I hope I did not lose or betray some of the meaning, it's hard when you don't get the finer points of the text… but you get the idea anyway!)