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Genetic research is not limited to work such as cloning and the investigation of human genetic disorders. These are certainly important aspects of the field, but there is much more to discover in the world of current genetic research. Here’s a small sampling of what’s been going on in genetics over the last year—note that some of the most interesting and potentially important discoveries are being made in some rather unexpected organisms!
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Gene Expression is Heavily Influenced by the Biological Clock
At the University of Georgia, genetic researchers are studying the link between genetics and the biological clock. The director of the project, Jonathan Arnold, says, “We found that some 25 percent of the genes in our model organism appear to be under clock control." The model organism is a variety of bread mold called Neurospora crassa, and the research team found that expression of nearly 300 of the organism’s genes is controlled by its biological clock.
It might seem somewhat irrelevant—it’s only bread mold, after all. But in fact, the biological clock is something which is common to all species of life, and the unknown mechanism which makes that clock tick is universal.
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DNA Repair Mechanisms and Genome Repeats
At the Duke University Medical Center and at the National Institute of Environmental Health Sciences in North Carolina, researchers have been studying the mechanism and effects of DNA repair in yeast. The researchers used x-rays to “break" yeast chromosomes and then study how the DNA was repaired. During this work they noticed that breakages were more likely to occur at repeat sequences, and that DNA repeats on different chromosomes would often join together to form entirely new chromosomes.
The genomes of higher species tend to have very high levels of repeated DNA sequences—humans have the highest percentage of all. The yeast research has shown that these repeats may be an important evolutionary mechanism which allows for diversification of the genome of a species. On very rare occasions, the breakage of the DNA—and the rearrangement to form a new chromosome—could be highly beneficial in evolutionary terms, and is also a mechanism by which new species can develop.
This work also has relevance to cancer research, because a large proportion of solid tumors have gene rearrangements of the type which could have been caused by this form of chromosomal rearrangement.
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Epigenetic Human Genome Changes over a Lifetime
In June, researchers at Johns Hopkins announced that they had found evidence that the human genome changes over time—that over the course of an individual’s life, the genome undergoes significant changes.
One way in which the genome is regulated is via methylation—the addition of a methyl group—of base pairs. Levels of methylation vary from one person to the next, and it’s been proposed that methylation and other mechanisms of genome change can contribute to disease development. In an eleven-year study of a population of Icelandic people, the researchers found that the degree of methylation of the genome changed over time—in some people the level was reduced, in others it increased. In addition, a further study of family groups in Utah found that members of the same family tended to have similar patterns of DNA methylation over time.
These are called epigenetic changes, and can be caused by environmental factors such as diet and toxin exposure. Epigenetic changes may play a role in diseases such as cancer and diabetes, and other diseases which have both genetic and environmental causes. They are also implicated in adult-onset diseases, and may cause the increased susceptibility of certain diseases which occurs as a result of aging.