Monohybrid Cross Problem Set

Problem 3: Mendel's "Experiment 1"

Tutorial to help answer the question

In Mendel's "Experiment 1," true-breeding pea plants with spherical seeds were crossed with true-breeding plants with dented seeds. (Spherical seeds are the dominant characteristic.) Mendel collected the seeds from this cross, grew F1-generation plants, let them self-pollinate to form a second generation, and analyzed the seeds of the resulting F2 generation. The results that he obtained, and that you would predict for this experiment are:

Tutorial

F1-generation plants

Mendel crossed SS (spherical seeds) with ss (dented seeds.)

All of the gametes of the spherical seeded parent have the S (dominant) allele and all of the gametes of the dented seeded parent have the s (recessive) allele. All of the F1 generation plants will have the genotype of Ss (heterozygous), and all will be spherical seeded.

**F1 generation**
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F2-generation plants

Mendel let the F1-generation plants self-pollinate to form a second generation and he analyzed the seeds of the resulting F2 generation.

F2 generation

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All F1-hybrid plants have the genotype Ss and all are spherical (dominant characteristic). The recessive alleles segregate during gamete formation. As a result, one out of four possible combinations of F2-generation plants will have the homozygous recessive genotype (ss).

The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
Thursday, October 1, 1998
Revised: November 2004
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