The Genetic Basis of Adaptive Melanism on Pocket Mice Essay examples --

Introduction What's the problem? Examples of animals adapting to the environment have been known as far back as the case of the black peppered moths of England in the mid-1800s. In that case, entire populations of the black peppered moths were observed to change color in response to changes in their environment. More recently, bacteria have been known to develop resistance to antibiotic drugs, insects have developed various forms of resistance to insecticide, and plants have adapted to accommodate higher levels of heavy metals in the soil and water. The problem is that it is difficult to locate the genes that stimulate adaptation for three reasons: 1. Traits must be identified based on how they affect fitness and their ecological relevance. In other words, we need to find a trait that clearly makes a difference in whether or not the animal survives. 2. It is challenging to analyze phenotypes when there is little information known about genes. With the moths, nobody knows which of the moth's genes are responsible for the changes in color, so a genetic analysis is extremely difficult to do. 3. Most fitness-related traits are a mixture of many genes. This makes it hard to pin down the adaptations as a result of the actions of one gene. So where do the mice come in? Dr. Nachman's research explores the connection between genotype and coat color in four populations of rock pocket mice. Rock pocket mice live in rocky habitats in the southwest U.S. and northern Mexico. In the 1930s, classical studies revealed that there was a close correlation between the color of a mouse's coat, and the color of the rocks the mouse lived on. Light-colored mice... ...is mice, the alleles did not appear to be responsible for any changes in coat color. The similarity between coat color of the dark mice at Pinacate and the dark mice at Armendaris is probably due to convergent evolution. The Armendaris mice probably evolved the same adaptation (dark coat color) through a separate genetic mechanism. An interesting research project might be to determine the genetic basis of adaptation in the Armendaris population, and make comparisons. Any such results would be enormously useful in showing how evolution affects individual genes. References Nachman, Michael W. Hope E. Hoekstra, Susan L. D'Agostino. "The genetic basis of adaptive melanism in pocket mice." www.pnas.org/cgi/doi/10.1073/pnas.0431157100. Feb. 26, 2003. Purves,William K., et al. Life: The Science of Biology Sixth Edition. Massachusetts: Sinauer Assoicates, Inc. 2001.