By Molly C-U, 7th grade
In 7th grade we started our zebrafish Lab. The point of the lab is to teach us about zebrafish and introduce us to the genetics of inheritance. Tracy Nelson from Penn’s Institute of Regenerative Medicine explained why zebrafish are a model organism in genetic research. For example, zebrafish are 70-75% genetically similar to humans, they develop diseases like us, such as cancer; they produce many offspring (which produces a lot of data), they have clear embryos, and are cheap to care for. In addition, their embryos develop and hatch into larva within a few days, so we can conduct the experiment in just one week.
After reviewing the procedure for setting up mating tanks, each group was given three zebrafish: one male albino, one female albino, and one female wildtype. We were asked to observe the fish and hypothesize about whether the male would be more successful in mating with the albino or the wildtype female, and based on the mating, what percentage of the offspring would be albino and wildtype. (In the past, students crossed just one male and one female. This is the first time that two females are being used -- even Tracy has never done this cross before -- so there are many unknowns!) While observing, we had to draw the fish in our lab books. To help identify them, we learned that the males were longer and thinner, whereas females had bigger bellies to carry the eggs. We also described behaviors, movements, and interactions among the fish.
In my group’s tank I observed that the wildtype female was darting around with sharp, fast movements. The male didn’t seem to be interacting with either of the females, and swam around calmly and slowly. The albino female was slower than the wildtype, but faster than the male. I hypothesized that the male would be more successful in mating with the wildtype female, but that the eggs would be 85% wildtype and 15% albino. The male would be more likely to mate with the wildtype female because he would recognize her as a healthy, functioning female.
Below are photos from the first day of the zebrafish lab.