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A complete understanding of evolution requires knowledge that spans many biological sub-disciplines. However, students are often taught evolution in the context of ecological systems and isolated from genetic and cellular ones. To address this issue, we have developed case studies that track the evolution of traits from their origination in DNA mutation, to the production of different proteins, to the fixation of alternate macroscopic phenotypes in reproductively isolated populations. You can navigate through the case studies using the menu at the top of the page. A short abstract of each case is provided below with links to PowerPoint slides that are designed to be teaching resources for those who wish to implement one or more studies into their teaching. |
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Monkey Opsins
Some monkey species have trichromatic, full color vision whereas others have dichromatic, red-green colorblind vision. Trichromatic monkey species can produce three types of transmembrane opsin proteins in the cone cells of their eyes; dichromatic monkey species only produce two types. This case examines the genetics, cell biology, ecology and phylogenetics of this system.
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Pea Taste
The common field pea (Pisum sativum) is one of the first plants to be domesticated as a crop, dating back to the Neolithic agricultural revolution, 10,000 BCE. They are the same species that Gregor Mendel, the father of modern genetics, used in his experiments when he discovered the laws of genetic inheritance. Wrinkled peas are sweeter than round peas because, as a result of an insertion mutation, they lack a functional starch branching enzyme. This case examines the genetics, cell biology, Mendelian connections and population genetics of this system.
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Mouse Fur Color
The beach mouse, (Peromyscus polionotus) is a small rodent found in southeastern United States. There are several sub-species that have different fur colors ranging from light to very dark. Beach mice with light fur often have a single nucleotide substitution mutation in their melanocortin 1 receptor gene that affects their ability to produce the dark fur pigment eumelanin. This case examines the genetics, cell biology, ecology and population genetics of this system.
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Toxin Resistance in Clams
Soft shell clams (Mya arenaria) are bivalves native to the east coast of North America. They are susceptible to paralytic shellfish poisoning caused by a poison, saxitoxin, that is produced by dinoflagellates during algal blooms. However, some clams have an nucleotide substitution mutation in a voltage gated sodium channel gene that makes them resistant to saxitoxin poisoning. This case examines the genetics, cell biology, ecology and population genetics of this system.
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Citrate Use in E. coli
Since 1988, Dr. Richard Lenski has been conducting a long-term evolution experiment using the bacteria E. coli. Sixteen years into his experiment, one of his twelve identical-but-separate E. coli colonies spontaneously evolved the ability to digest citrate under aerobic conditions. This case examines the genetics, cell biology, ecology and phylogenetics of this system.
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Lactose Metabolism in Humans
Nearly 65% of humans cannot digest the sugar lactose as adults. When lactose is not broken down in the gut, osmosis occurs to dilute its high concentration in the intestine. The high volume of water leads to cramping, bloating, and diarrhea. Furthermore, bacteria within the intestine ferment unused lactose, releasing high volumes of gas that cause further discomfort and flatulence. A single nucleotide polymorphism in a regulatory region of the lactase gene allows the transcription of the lactase-mRNA into adulthood, resulting in a trait called lactase persistence. This case examines the genetics, cell biology, anthropology and biogeography of this system.
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Skin Pigmentation in Humans
Human populations display a continuous palette of skin colors, with ancestral populations near the equator having darker skin and those evolving at higher northern latitudes having lighter skin. This case addresses the distribution of skin color in terms of natural selection and population genetics. Key genes and proteins for the synthesis and regulation of pigments are examined, with the complexity of a polygenic characteristic, such as skin color. Additionally, both the biological and societal notions of race, often based on skin color, are introduced.
This case is presented in a series of six PowerPoint slides:
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