sequence analysis

Would you like to have some fun playing with chromatograms and helping our class identify bacteria in the dirt? This quarter, my bioinformatics class, at Shoreline Community College, will be working with chromatograms that were obtained by students at Johns Hopkins University, and graciously made available by Dr. Rebecca Pearlman. (See see "Sequencing the campus at the Johns Hopkins University" for more background.) We are going to do a bit of metagenomics by using FinchTV and ... Read more
During the past few Fridays (or least here and here), we've been looking at a paper that was published from China with some Β-lactamase sequences that were supposedly from Streptococcus pneumoniae. The amazing thing about these particular sequences is that Β-lactamase has never been seen in S. pneumoniae before, making this a rather significant (and possibly scary) discovery ... Read more
One of my readers asked: Why does genome sequencing cost so much? My short answer is because it's big. But I thought it would be fun to give a better answer to this question, especially since I'm sure many of you are wondering the same thing. Okay, so let's do some math. Don't worry, this math isn't very complicated and I'll explain where most of the numbers come from. Estimating costs from salaries First, we'll take the easy route. My experience with grant budgets has taught me that the greatest cost for any project comes from salaries. If ... Read more

If you've read any of the many stories lately about Craig Venter or Jim Watson's genome, you've probably seen a "SNP" appear somewhere. You may be wondering, and rightly so: just what is a SNP?

Never fear, hopefully this post will answer some of those questions.

SNP stands for Single Nucleotide Polymorphism. That's a mouthful. It means some people, will have one base at a certain position, in a sequence of bases, and other people will have a different base at that position. The two forms of SNP are called "alleles." (Usually there are two forms, but that's ... Read more

"Come quickly, Watson," said Sherlock Holmes, "I've been asked to review a mysterious sequence, whose importance I'm only now beginning to comprehend." The unidentified stranger handed Holmes a piece of paper inscribed with symbols and said it was a map of unparalleled value. Holmes gazed thoughtfully at the map, then slowly lifted his eyes and coldly surveyed his subject's beaming countenance. "You have an affinity for the ocean," said Holmes, "that you indulged to excess as a reckless youth. An experience as a medic in the military changed your ... Read more
Why the ABRF of course!i-8b04187b7fb64bd408c576af1e9411ee-trace.gif I spend a fair amount time every summer giving workshops for college and high-school teachers on genomics and bioinformatics. One of the things that always surprises them, is the amount of lab work that's carried out by people working in shared, or core lab facilities. For example, if I was working at a research university and I wanted to sequence some DNA, maybe ... Read more
I began this series last week with a question about a DNA sequence that was published and reported to be one the first beta-lactamases to be found in Streptococcus pneumoniae. Mike has a great post about one of problems with this paper. I think the data themselves are awfully suspicious. So, last week I suggested that you, dear readers, go and find out why. I gave you a ... Read more
If you've read the previous posts on this topic, here and here, you're probably aware by now that I have this weird (okay, maybe fanatical) obsession with data. Or at least, with knowing if my data are right so I can get on with life, do the analysis and figure out the results. My results from last week suggested that re-processing chromatogram data (from the ABI 3730) ... Read more
One time I was watching a football game on TV and they had a short quiz, called "You make the call" or something like that, and you had to watch a play and pretend to be a referee. A short video clip showed football players falling over each other. Then you were three possible calls that a refereee might make and asked to chose which was correct. After the commercial, the announcer would tell you which choice was right and explain why it was correct. I suppose this was a trick to make us watch the commercials, but I thought the game was kind of fun. My SciBling "Mike the Mad" had a great ... Read more
Sometimes asking a question can be a mistake. Especially when your question leads to more questions and having to question things that you didn't want to question, and pretty soon you begin to regret ever opening the file and looking at the data and asking the question in the first place. Sigh. Take a deep breath. Yesterday through a twist of fate, I ended up taking a look at the DNA sequences produced by two different base calling programs from the same chromatogram file, from an ABI 3730 DNA sequencing instrument. I thought they would be the same, or at least similar.

... Read more

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