Lab Report

Introduction

Gregor Mendel has been famed for his genetics research using the common garden pea (Pisum sativum L). Since Mendel’s investigations into the genetics of the garden pea, research in this subject area has flourished and continues to be observed and tested. The pea plant itself has many genetic markers, making observations and predictions on phenotype possible. This type of genetic research has helped doctors predict likeliness of an offspring to have a predetermined ailment based on the parents’ genotype. (NIU Department of Biological Sciences)

The experiment described in this report was performed to investigate Mendel’s theory of the monohybrid and dihybrid cross. Using a punnett square (figure 1 and 2) we expect to see a 3:1 dominant to recessive ratio of a monohybrid cross and a 9:3:3:1 ratio of a dihybrid cross. This expectation is based on the theory of Mendel and his investigations on genetics.

Figure 1: Example of a punnett square showing a monohybrid cross.

Figure 2: Example of a punnett square showing a dihybrid cross.

Materials and Methods

Sixty plants (F2 Generation) Pea plants

Punnett square Used for monohybrid and dihybrid cross analysis

X²= (observed-expected)²/Expected Chi-Square formula

Sixty pea plants from the F2 generation were set up and observed for the following traits: stipules, leaflets, tendrils, and dwarfism. Since the plants were already potted and growing, seed color (Ii) and seed texture (Rr) was given. Dominant traits included plants that possessed stipules (St), leaflets (Td), tendrils (Tl), and long internodes (Le). Recessive traits included those plants that did not possess stipules (st), leaflets (td), tendrils (tl), and long internodes (le). Observations on all sixty pea plants were documented. These observations were then counted and...