INTRODUCTIONINTRODUCTION

HeredityHeredity, or the passing of traits from parents to , or the passing of traits from parents to offspringoffspring

Gregor Mendel was born is Heinzendorf, Austria in 1822 on a farm where he learned about flowers and fruit trees.

When he was 21 he entered a monastery.

The monks taught science and performed many scientific experiments.

Mendel discovered the principles of heredity in the monastery garden.

Unraveling the Mystery• From working with plants, Mendel

knew that the patterns of inheritance were not always clear.

• For example, sometimes a trait that appeared in one generation (parents) was not present in the next generation (offspring).

• Mendel decided to study garden peas to learn what caused the pattern of the peas in each generation.

Why PEAS?

Pea plants grow quickly (in a garden).

Pea plants are cheap.

Many different kinds (of traits or characteristics).

No ethical questions.

Can self-pollinate.

Self-Pollinating PeasSelf-Pollinating Peas

A self-pollinating A self-pollinating plant has both male plant has both male (pollen) and female (pollen) and female (ovule) reproductive (ovule) reproductive structures.structures.

Because the peas Because the peas were self-pollinating, were self-pollinating, Mendel was able to Mendel was able to grow a true-breeding grow a true-breeding plant.plant.

True True -- BreedingBreeding PlantPlant

When a true-breeding plant self- When a true-breeding plant self- pollinates, the offspring will have the pollinates, the offspring will have the same trait as the parent.same trait as the parent.

For example, a true-breeding plant with For example, a true-breeding plant with purple flowers will always have offspring purple flowers will always have offspring with purple flowers.with purple flowers.

Characteristics

• A characteristic is a feature that has different forms in a population.

• Mendel studied only one characteristic at a time.

• The different forms (such as round peas and wrinkled peas) are called TRAITS.

Mix and Match

• Mendel decided to see what would happen if he crossed two plants that had different traits of a single characteristic.

• He removed the anthers of purple flowered plant so that it could not self-pollinate, and cross-pollinated it with a white flowered plant.

Mendel’s Experiments

Traits

• A dominant trait is the trait observed in the first generation when parents that have different traits are bred.

• A recessive trait is a trait that reappears in the second generation (after disappearing in the first generation) when parents with different traits are bred.– To recede means “to go away or back off.”– The “hidden” trait.

TRAITS

Gone but Not Forgotten

In 1865, Mendel published his findings, however, it wasn’t until 30 years after he had died that his work was widely recognized.