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Paul Grobstein's picture

Bio 103, Lab 10: Genes, Environment, Selection

Last lab, we studied inheritance and recognized that there is an important distinction between genotype and phenotype. This week we want to look at the role that genes, environmental factors, and selection play in an organism's phenotype. To do so we will look at the phenotypes of populations of the plant Brassica rapa ("fast plants").

The plants you'll be looking at were all seeded at the same time several weeks ago. There are two genetically different populations (A and B) and each was grown under four different conditions (high light and fertilizer, low light and high fertilizer, high light and low fertilizer, low light and low fertilizer). To get started, examine specimens of each with the following questions in mind. Neither population is genetically homogenous, so keep in mind that there may be some variation due to unknown genetic factors.

  • Do genes affect plants?
  • Do environmental variables affect plants?
  • Are there characteristics that are affected only by genes, only by the environment, by both?

The answers to these questions are likely to be different for different plant characteristics. After looking generally at the plants, pick several different qualitative and/or quantitative characteristics to study in more detail. Among the latter, include a particular quantitative characteristic of these plants: the number of petiolar trichomes on the first true leaf. Describe relevant observations and interpretations in the lab forum area.

We will compare data on the number of petiolar trichromes in our plants with data from other laboratories in populations derived from ours by using as parents only those individuals having a number of trichomes greater than 90% of the population to determine if this characteristic is subject to evolutionary change.

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multiyearheritability.xls29.5 KB

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