mendel and his peas. the passing of traits from parents to offspring

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) true-breeding 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)