Show Me The Science Month Day 23 Installment 23



Thanks to your parents, you have two copies of each chromosome, which means that you have maternal and paternal copies of every gene. In most cases, having two copies of a gene is no problem, but in some cases, two is too much, and your cells have to shut one copy down. How does a cell do it?

Shutting down one copy of a gene (or an entire section of a chromosome) is called genomic imprinting. (This is not the same thing as the newly hatched duckling that latches on to the first thing it sees, obviously). Genomic imprinting is a critical process used by placental and marsupial mammals to control the dosage of many genes, but how did this process evolve?

The answer, in part, has been discovered by an analysis of the platypus genome. Genomic imprinting appears to have evolved from a defense mechanism used by cells to knock down parasitic DNA.

Show Me The Science Month Day 22



How do genes work together to build body traits? This is one of the hottest questions in genetics today, and the answer holds implications not only for our understanding of evolution, but also health, agriculture, and wildlife conservation. A recent paper in Science (by Scientific Blogging's own Redneck Geneticist) takes a look at how genetic variants work together to generate the physical diversity that we see in living organisms.

Show Me The Science Month Day 21



Why do certain species of fruit flies prefer some fruits over others? Two biologists have looked at the genetic basis behind the evolution of fruit preference, in a paper in this month's issue of Genetics (an incredible issue which happens to contain another amazing, pioneering, paradigm-shifting, ground-breaking paper).

Many insects specialize in feeding on just one or a few types of plants. This fact isn't that surprising, since plants have all sorts of defenses for warding off insects, including the production of toxic chemical compounds, and insects that feed on plants have typically evolved ways to get around the defenses of one type of plant, but not another. This phenomenon is dramatically played out in the hundreds of species of fruit flies around the world, many of which specialize in just one or a few types of fruit. Researchers at Michigan State and UNC Chapel Hill have looked at the genetic changes that enabled one species of fruit fly to specialize in the fruit of the Morinda plant, also known as cheese fruit, a fruit that is toxic to other flies.



Morinda citrifolia, photograph by Eric Guinther

Over at the Chronicle of Higher Education, Columbia University humanities professor Andrew Delbanco takes stock of recent arguments that the intellectuals are back in charge of government:

What goes on here? Was the historian Richard Hofstadter wrong in his classic Anti-Intellectualism in American Life to detect an irresistible current in our society of "resentment and suspicion of the life of the mind and of those who are considered to represent it"? Has that current weakened or been sufficiently dammed up to explain the election of a president who is reflective about history and ideas as well as about policy and practice?

Show Me The Science Month Day 20



Tumor cells wield the enzyme heparanase like a machete to cut a swath
through the dense forest of carbohydrates that make up the sticky
matrix that helps hold communities of cells into tissues. Aggressive,
metastatic tumor cells have to break free of the confines of this
extracellular matrix in order to both grow and colonize new parts of
the body. In humans, heparanase is expressed at high levels in tumor
cells, and it therefore makes an attractive drug target: knock out
heparanase, and tumor cells can't bushwhack their way out of the
confines of the extracellular matrix.

A group of Israeli researchers has discovered a defective form of heparanase in blind mole rats, animals which spend their whole lives underground and as a result have adapted to deal with low oxygen conditions that parallel conditions experienced by tumor cells. This defective form of heparanse could become a new tool in the cancer treatment toolbox.

Show Me The Science Month Day 19



Some fish have two sets of teeth: oral teeth, set towards the front of the mouth (like ours), and so-called pharyngeal teeth, set far back in in the throat in a strange, second set of jaws. Based on what we learn from the fossils of ancient jawless fish, it appears that teeth first appeared on these deep pharyngeal jaws. So how did most vertebrates come to have the more common set of oral teeth? A group of scientists based in Georgia and Tennessee used paleontology and modern genetics to show that tweaks to an ancient gene regulatory network enabled the evolution of  oral cavity teeth possessed by most vertebrates.



Figure 1 from Fraser, et al.