Mendel and his Peas The passing of traits

Mendel and his Peas

The passing of traits from parents to offspring.

Gregor Mendel • • Born 1822 in Austria At 21 became a monk Went to school in Vienna Conducted his own scientific investigations in the monastery garden.

Mendel’s Experiments • Kept them simple and “controlled” • Kept very good records • Worked with pea plants

Mendel’s Experiments continued… • He observed characteristics including seed shape, plant height and flower color. • Only observed one characteristic at a time. • A characteristic is a feature that has different forms in a population. • Traits are the different forms that a characteristic can take.

Mendel’s First Experiment • Created true-breeding plants before he started his experiments (He did this by breeding the plants for many generations until he always got the expected results. ) • When one true-breeding plant self pollinates all of the offspring will have the same traits as the parent.

Mendel’s First Experiment continued… • He crossed (cross pollinated) truebreeding purple flowers with true-breeding white plants. • He removed the anthers of one plant to make sure that they cross pollinated.

All of the offspring were purple

Mendel’s First Experiment continued… • The purple flower was always present while the white flower seemed to disappear. • He said the purple flowers was a dominant trait and the white flower was a recessive trait.

The same was true for the pea pod experiments.

Mendel’s Second Experiments • He allowed the first generation plants (offspring of the first experiment) to self pollinate. • The recessive trait reappeared in the second generation. • He noticed a 3: 1 ratio of the dominant to recessive traits. • This ratio showed the relationship between two different things (traits)

Mendel realized… • His results could only be explained if each plant had two sets of instructions for each characteristic. • Each parent would donate one set of instructions but only one would show up in the offspring.

Use a Punnett Square to calculate the probability that offspring with a certain characteristic will result.

First Generation (two true breeding parents)

Second Generation (both parents are not true breeding)