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Protists, UV and Evolution

by Dr. Lynn Rothschild
Research Scientist, NASA Ames Reseacrh Center

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Protists include protozoa, alge and some fungi. All eukaryotes are either protists or descendants of protists. Phylogenentically, plants are a small sub-group of the green algae!. Protists are a very diverse group. There are many reasons to study protists: as model systems for ecology, for examining cell structure and the history of evolution. The fossil record tells us that protists are about 2 billion years old and are really sort of "it" until the Precambrian period.

Dr. Rothschild's research at Ames has been to try to model the Precambrian environment for a protist. She is using modern analogs to study photosynthesis using radiactive carbon to trace changes in carbon dixodie production. More recently she has studied the role of ultra-violet light in influencing evolution.

Fluctuations in UV light can be very important in evolution because DNA naturally absorbs energy in the UV-C region and proteins absorb energy close to the UV-B range. DNA and proteins are very susceptible to UV damage. UV also effects algae and phytoplankton be inhibiting photosynthesis in both the light and dark reactions and nitrogen fixation. Some of the effects can be mutations as well. Damage to DNA can be studied experimentally in the field. One important point is to look at the relationship between DNA synthesis (or repair) and the time of day.If increases in DNA synthesis are correlated with a period of daylight associated with increased amounts of UV light, this can be studied in the laboratory and evaluated as excision repair or as some other process.

DNA repair is the result of a multiple of problems. Could UV radiation be a driver for molecular evolution? In conclusion, the answer is possibly "yes".

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