Take a good, hard mental image of a long line of people stretched for blocks. If you expand the line to roughly 100,000, this is the number of people waiting for an organ transplant. The imbalanced patient-to-organ ratio leaves many to die while waiting their turn. In response, some researchers try to tap into animal organs to save human lives, but those organs do not always work.
Research in the University of Missouri’s Division of Animal Sciences may help solve this medical debacle by using genetic modification. When an organ goes from one animal to another (like to a human), preexisting antibodies in the human bind to the organ’s sugar molecules and kill the organ, making it useless. “When you take a pig cell and transfer it to a human, the molecule is immediately recognized as foreign,” explains MU’s Animal Science Professor, Randall Prather. “Within minutes you’ll get hyperacute rejection, and the cells will be destroyed.”
Cone’s current research seeks to understand the function of a group of genes called chromatin: “Chromatin is the complex of DNA and protein, which allows us as humans–or plants like corn–to pack a lot of DNA into the tiny nucleus of a cell.” The DNA duplex for both corn plants and humans is huge. As she explains, “we have about the same size genome, about three billion base pairs, but ours is really long. We pack about six feet of DNA in every cell,” each of which is only five microns across. That’s a heck of a lot of DNA!” How does all that DNA fit in there? “We’re smart,” suggests Cone, adding that “corn and humans do it the same way,” as does every organism with a nucleus. Therefore, her research on DNA packaging is applicable to every organism, because “from yeast, to mice, to humans, to plants—we all wrap up our DNA basically the same way.” It amounts to a sort of microscopic compressor system, which Cone describes as “amazing.” If researchers can better understand how this chromatin packaging occurs, they might eventually be able to control the process to their advantage.
Cone responds to some basic questions about doing genetics research with plants, discussing such matters as reporter genes, gene activity, pigmentation, and the impact of environmental factors on the research.
This research on DNA packaging is applicable to every organism, Cone observes. Using the example of a calico cat, she explains: “Tortoise-shell and calico cats have orange and black fur patches on their body. That is due to a DNA packaging phenomenon.” As it turns out, the fur color gene is on the X chromosome. Just as human females have two X chromosomes, so do these calico cats, which are almost always female. In fact, they have one X with an orange-fur gene and one X with a black-fur gene: “so back when that little calico cat, with her different X chromosomes, was a 16 or a 32-cell embryo, in each cell, one of the X chromosomes got really tightly packaged, so tightly that the genes on that chromosome weren’t expressed.” If the X with the orange-fur gene is packaged, she continues, then the X with the black-fur gene remains active. As the cell divides further in the embryo, it will eventually give rise to a black patch of fur. The orange patches, of course, derive from the fact that in another cell, the X with the orange-fur gene, was the one left active, while the black one was balled up too tightly to be expressed. That is one concrete example of how DNA packaging influences whether or not a gene is turned on.