The microarray data will tell you what class of chemical is in the water. There are four potential suspects:

  1. Metal: There is evidence of an old chromium mine upstream. Chromium may be leaching into the stream water.
  2. PCBs (polychlorinated biphenyls): PCBs are a class of chemicals. These fire-resistant compounds were used as insulation in electrical transformers. Last winter, a strong storm caused an old power line to crash down near the river and leak PCBs onto the riverbank.
  3. Environmental estrogen: At a park next to the stream, the local mosquito control program began using an insecticide called methoxychlor which has effects similar to natural estrogen
  4. Retinoid: Methoprene, an insect growth regulator, was also used in the mosquito control program. In the environment, methoprene breaks down into compounds called retinoids. This class of compounds includes natural substances like vitamin A which at high doses can cause birth defects.

mRNA collected from
zebrafish embryo tissue

You will compare mRNA from the experimental treatment embryos and the control embryos. To look at changes in gene expression, you will extract mRNA from the two embryos and analyze them with the microarray.

Your job is to determine what type of compound is causing the deformed fish.

Microarrays: How do they work?