We made F1 diploid sporophytes by crossing a haploid green parent with a haploid pale parent. All of the F1 sporophytes were green; they had one allele for green and one for pale (green is dominant). Since the alleles separate independently, the diploid parents give one copy of the allele for color to one gametophyte and the other copy to another gametophyte. This is why we see some pale gametophytes and some green gametophytes. According to our hypothesis for Hybrid A and Hybrid B, after we allow random fertilization among the G2 population, we should have noticed more green plants than pale plants in the F2 sporophyte population. We induce fertilization among the plants by placing a small amount of water on the ager plates where the gametophytes were growing. This alloed the sperm to move freely around the plant and insured random fertilization.
Materials and Methods.
During week one we were given two-week-old cultures of G2 C-Fern gametophytes. The cultures were grown on agar plates marked A and B. The plates were maintained at 28o Celsius. The plates were also kept under 24 hour fluorescent light for two weeks. We counted the number of pale and green hermaphrodite gametophytes. In order to make counting easier we drew a grid on the plate, which kept us from double counting, and placed it under a dissecting scope. We only counted hermaphrodites because they are much larger and more easily; they are also the ones that go o n to produce the F2 generation. This created a standard so the class results could be compiled and the data would not be skewed. We compiled the class data to increase our sample size. An increased sample size helps us test our results against expected ratios more accurately. These numbers gave us an indication of how many green and pale sporophytes we would have once the gametophytes were given a chance to undergo fertilization. We placed 2 mL of sterile water on each of our agar plates to induce random fertilization among the haploid gametophytes.