The animal with the most genes: A new (and unexpected) record holder

FRESH OUT OF THE PRESS!!!

Water flea, Daphnia pulex
Picture published by NPR.org
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A new complete genome has been sequenced and a new surprising fact was unveiled: The new record holder for having the most genes among animals is the very tiny water flea, Daphnia pulex (Crustacea: Branchiopoda: Cladocera). It has approximately a whooping 31,000 genes! (compared to about 23,000 in humans). Their genome, nevertheless, is not too big, which makes the surprise even bigger: It is about 200 million base pairs (compared to the 3 billon in the human genome).

This is another example of how size and morphological complexity are poor predictors of genome size or number of genes (and viceversa). Water fleas are typically no more than a few millimeters long and, to the unaware, rather unremarkable little fellows. However, they are physiologically very complex, and this seems to be the reason for which they have accumulated so many genes over evolutionary time.

Yet another surprise that the growing field of Genomics has given us.

Click here for an extended version of the news on NPR.org.

Click here to access the abstract of the original paper on Science Magazine.

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Exam 2

Stats for exam 2:

(click on pic for full size image)

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Module 3, Lab 12 pGLO Small Scale Plasmid DNA Purification and Restriction Enzyme Digestion (RED)

pGLO plasmid and restriction map
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Today we used the bacteria we transformed with the pGLO plasmid and cloned a few weeks ago to perform a small scale plasmid DNA purification (minipreps) and isolate the pGLO plasmid again.

Then we performed a restriction enzyme digestion, RED, using the restriction enzymes EcoRI and HindIII (see restriction map).

(note: section 2 performed these procedures on Monday)

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LectureChapter 10 - Gene regulation in eukaryotesChapter 11 - Regulation at the RNA level

Today we talked about the important role that the histone remodeling complex plays in allowing proteins access to DNA in nucleosomes. We related the action of this enzyme, as well as HATs and HDs in the gene expression process as a whole.

We then discussed the role of methylation patterns in gene silencing and provided an example in genetic imprinting.

We also started a discussion on chapter 11, on how gene expression is regulated between transcription and translation (control at the mRNA level). We mentioned the several ways in which the translation of a mRNA molecule can be controlled, and then we focused in one of them: Controlling the stability and the rate of degradation of the mRNA (usually via ribonucleases a.k.a. RNases).

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