Polar lobes and trefoil embryos in the Precambrian

i-b275e2beecc20e27c50d7f1200419c67-dentalium_polar_lobe.gif

i-82a3d61658c78fe68f81f85cd6236021-lobed_embryo_tease.jpg

The diagram above shows the early cleavages of the embryo of the scaphopod mollusc, Dentalium. You may notice a few peculiarities: the first cleavage is asymmetric, producing a cell called AB and a larger sister cell, CD. Before the second division, CD makes a large bulge, called a polar lobe, and it almost looks like it’s a three-cell stage—this is called a trefoil embryo, and can look a bit like Mickey Mouse. The second division produces an A, a B, a C, and a D cell, and there’s that polar lobe, about as large as the regular cells, so that it now resembles a 5-cell embryo. What’s going on in these animals?

[Read more…]

Maternal effect genes

i-ccbc028bf567ec6e49f3b515a2c4c149-old_pharyngula.gif

Maternal effect genes are a special class of genes that have their effect in the reproductive organs of the mutant; they are interesting because the mutant organism may appear phenotypically normal, and it is the progeny that express detectable differences, and they do so whether the progeny have inherited the mutant gene or not. That sounds a little confusing, but it really isn’t that complex. I’ll explain it using one canonical example of a maternal effect gene, bicoid.

[Read more…]

Don’t delay, donate!

We have received most excellent news from Seed: notice that challenge bar to the left, where I (and many other science bloggers) are asking you to donate to public education? We’re doing great—my challenge has gathered over a thousand dollars so far, all to help out teachers and schoolkids—but now Seed has announced that they will match the total donations, up to $10,000. Double your money!

I’ve set a goal of raising $2000 for teachers, but I’ve got a dozen projects listed, and they’re going to need more than that if all are to be fully funded. If I hit the goal, don’t stop—you can keep contributing. Janet has a list of the other participants, too, so if you want to spread the joy around some more, check out the others.

Oh, and everyone should shout out, “Yay, Seed!” right now. It’s the right thing to do, even if it startles other people in the office or coffee shop.

It must be a universal property of creationists

Maybe I was too hard on Harun Yahya. As Wesley writes, plagiarism and theft are common practices among creationists—it’s even encouraged.

Authors such as George Macready Price and Henry M. Morris assembled many of the arguments together in various books. And, as I said, nobody cares if you steal it. In fact, others will be confused if you provide complete references and trace back claims to sources. That just isn’t done as a matter of course in this field, and, of course, it pays to pick up the social gestalt of your new career.

When among knaves and fools, do as they do.

Help teachers!

The scienceblogs crew is pushing a new charity for the next few weeks: an outfit called DonorsChoose, which collects funding requests from teachers and tries to match them up with people willing to pass along a few dollars. They have a long, long list of teachers looking for help in their classrooms; what we sciencebloggers have done is picked a subset of the requests that each of us like and grouped them into a challenge. My challenge contains a dozen science-related requests, and now my job is to beg you, the readers of Pharyngula, to take a look at them and if you can, kick in a few dollars to help them out.

If you look to the sidebar on the left, you’ll see a status bar showing how close we are to funding those requests. It’s at a pathetic 0% right now, but it would be nice to see it fill up.

I said that a lot of us here at scienceblogs are doing this; Janet has a complete list, so if you’d rather help out one of the other blogs meet their goal, please do. All that matters is that teachers get help, not which of us helps out.

Also, there will be a random drawing at the end of our efforts, and donors have a chance of winning various small tchotchkes. Again, Janet has the details, including the list of fabulous prizes.