Genomics Video 3
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Genomics Video 3


Genomics: Observing Evolution The Flaxman Lab at CU Boulder Biologists use genomics to observe and
study evolution in two main ways: field work, including experimentation in natural settings, and statistical inference. Field biologists can detect genetic changes
based on the observable traits they influence. Such work may span many generations of the organism being studied. One example is the study of finch species in the Galapagos Islands, beginning with Darwin and conducted for over a century. By noting differences in beak size and shape,
scientists observed both evolutionary changes within populations and the divergence of new finch species. But what about the second approach—statistical inference? Scientists using this approach observe patterns
of DNA sequences from current populations. They use those patterns to infer the most likely evolutionary processes
that resulted in the populations of today. Butterflies in the genus Heliconius are being studied by many scientists
from universities around the globe. Heliconius butterflies provide what is known as
a model system for genomic research. They are living today, they are abundant,
and they can be raised in laboratory conditions. In addition, their shorter lifespans allow scientists
to observe changes across many generations. Heliconius have brightly colored, boldly patterned wings,
which help them attract a mate. Some have wing patterns that mimic those of butterflies
that are distasteful to predators, an important evolutionary advantage. Since wing patterns that mimic bad tasting butterflies improve survival rates,
one might predict that there would be very few different color patterns. But, there is great variation in color patterns in Heliconius. This suggests that other evolutionary forces are at play. The Flaxman Lab at CU Boulder works with data
from several species of Heliconius from Costa Rica to understand the different evolutionary forces at work in this complex system. To do so, they develop computer simulations
of evolution over many thousands of generations, projecting both forward and backward in time. By identifying patterns in actual DNA
that are similar to those observed in simulations, they can infer that different parts of each species’ genome have effects that,
when combined, restrict the flow of genes between species. The combined effects of multiple genes working in concert
can speed up the rate at which new species form. It is one piece of the puzzle that explains the high species diversity
—and thus biodiversity—in nature. Advances in computational power and the tools to rapidly sequence genomes of
living species allow scientists to screen amazingly vast numbers of DNA sequences. This is an incredibly powerful way to look back at the past and project forward into the future. It allows us to understand the ability of organisms,
including humans, to adapt to a changing environment. The knowledge gained from such studies helps us understand our place
in the natural world and gives clues to the future of life on our planet.

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