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This is third video in our series on analyzing the DNA sequences that came from bacteria on the JHU campus. In this video, we use a pivot table to count all the different types of bacteria that students found in 2004 and we make a pie graph to visualize the different numbers of each genus. The parts of this series are: I. Downloading the data from iFinch and preparing it for analysis. (this is the video below) (We split the data from one column into three). II. ... Read more
yep, I've become a videoblogger, at least sometimes. See the first video below. Be kind in the comments, this is a new thing for me. This video introduces the different blast programs, discusses word size, and how blastn works, the blastn score and the E value. The treatment is light and not too in depth, but as I said, it's an introduction. ... Read more
A long standing debate in my field is whether or not biologists, who work with computers, need to learn how to program. I usually say "no." Let the programmers program, the biologists interpret the results, and let everyone can benefit from each other's expertise. Well, I've changed my mind in one respect. Most biologists need to work with some kind of database these days and I've discovered that it's really helpful to know something about SQL. Even a tiny bit of SQL, like "SELECT * from table" goes a long, long way. This revelation didn't happen overnight and when I ... Read more
DNA sequence traces are often used in cases where:
  1. We want to identify the source of the nucleic acid.
  2. We want to detect drug-resistant variants of human immune deficiency virus.
  3. We want to know which base is located at which position, especially where we might be able to diagnose a human disease or determine the best dose of a therapeutic drug.
In the future, these assays will likely rely more on automation. Currently, (at least outside of genome centers) many of these results are assessed by human technicians in clinical research labs, or DNA testing ... Read more
Last year I wrote about an experiment where I compared a human mitochondrial DNA sequence to primate sequences in the GenBank. Since I wanted to know about the differences between humans, gorillas, and chimps, I used the Entrez query 'Great Apes' to limit my search to a set of sequences in the PopSet database that contained gorillas, bonobos, chimps, and human DNA. A week ago, I tried to repeat this experiment and...

It didn't work.

All I saw were human ... Read more

Metagenomics is a field where people interrogate the living world by isolating and sequencing nucleic acids. Since all living things have DNA, and viruses have either DNA or RNA, we can identify who's around by looking at bits of their genome. Researchers are using this approach to find the culprit that's killing the honeybees. We're also trying to find out who else shares our bodies, and lives in our skin, in our stomachs, and other places where the sun doesn't shine. Craig Venter used ... Read more
The simple fact is this: some DNA sequences are more believable than others. The problem is, that many students and researchers never see any of the metrics that we use for evaluating whether a sequence is "good" and whether a sequence is "bad." All they see are the base calls and sequences: ATAGATAGACGAGTAG, without any supporting information to help them evaluate if the sequence is correct. If DNA sequencing and personalized genetic testing are to become commonplace, the practice of ignoring data quality is (in my opinion) simply unacceptable. So, for awhile anyway, I'm ... Read more
We have lots of DNA samples from bacteria that were isolated from dirt. Now it's time to our own metagenomics project and figure out what they are. Our class project is on a much smaller scale than the honeybee metagenomics project that I wrote about yesterday, but we're using many of the same principles. The general process is this:
  • 1. We sort the chromatogram data to identify good data and separate it from bad data. Informatics can help you determine if data is
  • ... Read more
The next time you bite into a crisp juicy apple and the tart juices spill out around your tongue, remember the honeybee. Our fall harvest depends heavily on honeybees carrying pollen from plant to plant. Luscious fruits and vegetables wouldn't grace our table, were it not for the honeybees and other pollinators. i-5b72428eaa872c6d705e8a3dfcbe8139-bee.pngLately though, the buzz about our furry little helpers hasn't been good. ... Read more
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

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