What are the independent and dependent variables in this experiment? Why is it important to test only one variable at a time? What other conditions might have an impact on the independent variable?
Fertility researches are concerned that man-made chemicals may reduce reproduction in animals. One of the most common herbicides, 2,4-D was tested to see if it prevented meiotic maturation of oocytes, a necessary step to make a fertilizable egg. The frog, Xenopus Laevis, was used a model system. Also, when Xenopus oocytes are incubated in a buffer containing the hormone, progesterone, they mature within about 6 hours. This is seen with a dissecting microscope by the appearance of a white spot in the pigmented part of the oocyte. To test the effect of 2,4-D, oocytes were divided into 4 treatment groups by placing 30 oocytes per dish into 4 petri dishes containing buffer. Three of these groups received either 1 microM progesterone, 10mM 2,4-D or a combination of 1 microM progesterone and 10mM 2,4-D. For each treatment a replicate was made. At 8 hours of incubation at room temperature, oocytes with white spots were counted and an average percentage maturation was calculated for each treatment group and was represented with a bar graph.
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