Lesson Overview The Work of Gregor Mendel

Objectives 11.1The Work of

Gregor Mendel

-Survey Mendel’s studies and conclusions about inheritance.

-Examine what happens during segregation.

Lesson Overview The Work of Gregor Mendel

What is heredity?

The delivery of characteristics from parent to offspring is called heredity.

The scientific study of heredity, known as genetics.

Lesson Overview The Work of Gregor Mendel

The Experiments of Gregor Mendel

The modern science of genetics was founded by Gregor Mendel.

Mendel used simple garden peas to demonstrate how traits are passed from one generation to the next.

Lesson Overview The Work of Gregor Mendel

Self Pollination

Pea flowers are normally self-pollinating, which means that sperm cells fertilize egg cells from within the same flower.

“True Breeding”

Lesson Overview The Work of Gregor Mendel

Cross Pollination

Mendel decided to “cross” his stocks of true-breeding plants—he caused one plant to reproduce with another plant.

The offspring of crosses between parents

with different traits are called hybrids.

Lesson Overview The Work of Gregor Mendel

The GenerationsWhen doing genetic crosses, we call the original pair of plants the P, or parental, generation.

Their offspring are called the F1, or “first filial,” generation.

The offspring of the F1 generation are the F2, or “second filial,” generation.

Lesson Overview The Work of Gregor Mendel

GenesFrom these results, Mendel drew two conclusions:

1. An individual’s characteristics are determined by factors that are passed from one generation to the next.

Scientists call the factors that are passed from parent to offspring genes.

Lesson Overview The Work of Gregor Mendel

AllelesEach of the traits Mendel studied was controlled by one gene that occurred in two contrasting varieties.

The different forms of a gene are called alleles.

Lesson Overview The Work of Gregor Mendel

Dominant vs Recessive Traits2. The principle of dominance states that some alleles are dominant and others are recessive.

An organism with at least one dominant allele for a trait will exhibit that form of the trait.

An organism with a recessive allele for a trait will exhibit that form only when the dominant allele for the trait is not present.

Lesson Overview The Work of Gregor Mendel

A capital letter represents a dominant allele.

A lowercase letter represents a recessive allele.

THEY MUST ALWAYS BE THE SAME LETTER.

Representing the Gametes

Lesson Overview The Work of Gregor Mendel

True or False

1. A trait is a specific characteristic that can vary from one individual to another. _________________________

Lesson Overview The Work of Gregor Mendel

Answers

1. A trait is a specific characteristic that can vary from one individual to another. True