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
University of Arizona
Thursday, October 1, 1998
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