Introduction to Genetics

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I. History of Genetics

•The monk, Gregor Mendel, was interested in heredity or how parents pass traits to their offspring.

•Mendel used garden pea plants to study heredity.

II. Garden Peas• Garden peas are self-pollinating plants.

They contain both male and female parts.

• Many of the traits of the garden pea plants are seen as one of two forms. Ex: the plant is either tall or short, the seeds are either round or wrinkled.

• Garden peas can self-pollinate or cross-pollinate.

III. Mendel’s first experiment

• Mendel crossed true breeding plants, which are plants that will always produce offspring with the same trait that the parent plant has.

• If the two plants had different forms of the trait, one of them always appeared in the offspring, the other one always disappeared.

• The trait that appeared is the dominant trait and the one that disappeared is the recessive trait.

IV. Mendel’s first experiment: an

example• Mendel took the pollen from a plant with round

seeds and fertilized a plant that had wrinkled seeds, these plants are the parent generation.

• The offspring are called the first generation, they all had round seeds.

• Round seeds are the dominant trait and wrinkled seeds are the recessive trait.

Mendel was lucky that he chose to work with the pea plant. The traits of the garden pea plant are either dominant or recessive, they do not blend like human hair or skin color.

V. Mendel’s second experiment

• Mendel allowed the first generation plants to self-pollinate.

• The dominant traits showed up again, but so did the recessive traits that has disappeared.

• The offspring of the second experiment are called the second generation.

VI. The second experiment: VI. The second experiment: an examplean example

Mendel took pollen from one of the first Mendel took pollen from one of the first generation plants (that had round seeds) generation plants (that had round seeds) and fertilized a plant from a first generation and fertilized a plant from a first generation plant (that also had round seeds).plant (that also had round seeds).

The offspring were 75% round or dominant The offspring were 75% round or dominant and 25% wrinkled or recessive.and 25% wrinkled or recessive.

VII. Mendel’s Conclusions!

• The only way that Mendel could explain his observations is that each plant must have two sets of instructions for each characteristic.

• One set of instructions comes from each parent.

VIII. What we know today

• Each parent donates one set of instructions called genes.

• The two forms of the gene that determine each characteristic are the alleles.

• In garden pea plants, the dominant allele for pea shape is round and the recessive allele for pea shape is wrinkled.

IX. Summary

Now that you have completed your notes, write your 5 sentence summary at the end of your notes.