INVESTIGATION OF THE INHERITANCE OF THE ROSETTE GENE IN BRASSICA RAPA

By: Justine Poorbaugh

Foundations of Biology 2 Laboratory
Thursday 2:30 PM
Professor Cheek
April 21, 2011

ABSTRACT

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
The phenotypes of the F2 generation were recorded in Table 3 and a chi square test was performed with the class results of the F2 seedling phenotypes.

Table 1: List of Activities for Investigation of the Inheritance of the Rosette Gene in B. rapa Approximate Day | Activity | Day 1 | Plant F1 hybrid seeds | Day 7 | Observe seedlings and record numbers of each phenotype. Thin plants to one exercise cell. | Day 14, 16, 18 | Cross-pollinate with the pollinating wand. | Day 18 to 32 | Remove any new buds and shoots. | Day 33 | Remove quad from watering tray. | Day 39 | Harvest F2 seeds and germinate in petri dishes. | Day 41 | Count and record numbers of each phenotype. |

RESULTS The class results from the cross between the true breeding standard and true breeding rosette forms of B. rapa were 43 standard plants, and 2 rosette plants. For the F2 generation, there were 41 standard and 13 rosette plants. There were approximately three times more standard plants than rosette plants in the F2 generation. The chi-square calculations produced an x2 value of 0.025.
Table 2: Phenotypes of F1 B. rapa Seedlings from Crosses Between Plants with Standard Form and Rosette Form (short) Number of Plants | Team | Standard | Rosette | Tuesday Morning Lab | 12 | 0 | Tuesday Afternoon Lab | 9 | 2 | Thursday Evening Lab | 10 | 0 | Thursday Afternoon Lab | 12 | 0 | Class Total | 43 | 2 |
Table 3: Phenotypes of F2 Seedlings Number of Plants