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11.3 Exploring Mendelian Genetics

11.3 Exploring Mendelian Genetics. Independent Assortment. Mendel performed an experiment to follow two different genes as they passed from one generation to the next. The two-factor cross: F1.

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11.3 Exploring Mendelian Genetics

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  1. 11.3 Exploring Mendelian Genetics

  2. Independent Assortment • Mendel performed an experiment to follow two different genes as they passed from one generation to the next.

  3. The two-factor cross: F1 • First, Mendel crossed true breeding plants that produced only round yellow peas (genotype RRYY) with plants that produced wrinkled green peas (genotype rryy) • This cross provides hybrid plants needed for the next cross-the cross of F1 plants to produce the F2 generation.

  4. The 2-Factor Cross: F2 • The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes. • Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms.

  5. A summary of Mendel’s Principles • Genes are units that determine inheritance of traits • Some alleles are dominant and some are recessive • In sexually reproducing organisms, each adult has 2 copies of each gene-one from each parent • alleles from different genes segregate independently

  6. Beyond Dominant and recessive alleles • Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

  7. Incomplete dominance • Cases in which one allele is not completely dominant over another are called incomplete dominance.

  8. Codominance • A similar situation is codominance, in which both alleles contribute to the phenotype.

  9. Multiple alleles • Many genes have more than two alleles and are said to have multiple alleles.

  10. Polygenic Traits • Traits controlled by two or more genes are said to be polygenic traits.

  11. Applying Mendel’s Principles • In the early 1900’s, geneticist Thomas Hunt Morgan was looking for an animal that was small, easy to keep in the lab, and able to produce many offspring in a short period of time.

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