By: Justine Poorbaugh
Foundations of Biology 2 Laboratory
Thursday 2:30 PM
April 21, 2011
The Brassica rapa is a rapid growing plant that has a standard form and a mutant rosette form. Relative to normal plants, the rosette form is shorter and takes longer to flower. The mode of inheritance of the rosette gene was tested by crossing two true-breeding plants, one of each form. The F1 generation was then cross-pollinated to produce an F2 generation. The phenotypes of each generation were recorded and a chi-square test was performed. The F1 offspring were almost entirely standard form, and the F2 followed the Mendelian ratio of three standard to one rosette. This supported the idea that the rosette allele is recessive to the standard form, and that it follows Mendel’s law of segregation.
The Brassica rapa is also known as a Wisconsin Fast Plant. This is because the plants complete their life cycle in approximately 35 to 45 days. The B. rapa are able to grow in potting soil kept at room temperature with only a common house plant fertilizer added to the soil. They also require continuous fluorescent lighting from conventional fluorescent bulbs (Williams and Hill, 1986). Due to the B. rapa having simple growth requirements and the inability to self-pollinate, they are an ideal organism for this experiment. Each individual plant will reject its own pollen, making it effortless to mate two individuals by transferring pollen from one to the other.
The rosette form of the B. rapa is caused by a single gene mutation that causes the plant to be shorter in relation to the standard plant form. The shortness is due to a deficiency in gibberellins. Gibberellins are hormones that stimulate stem elongation, and trigger the germination of seeds (Campbell and Reece, 2008). The mutant plants in turn germinate slowly, have delayed or incomplete...