Chapter 2 Lesson 4-Traits and Heredity
Vocabulary
1. Heredity
2. Inherited trait
3. Instinct
4. Gene
5. Dominant trait
6. Recessive trait
7. Pedigree
8. Carrier
NOTES
What is heredity?

Heredity is passing down of traits from parents to offspring.

Heredity applies to ALL organisms.

Flower color, flower height, eye or hair color are inherited traits (see vocab).

Heredity can affect an organism’s behavior (see Instinct in vocab).
o
Web building in spiders is an instinct.
o
Nest building.

A learned behavior is developed during the course of an animal’s lifetime.

Learning results from practice and experience.
o
Training a dog.

The ability to learn helps animals survive.

Imprinting occurs when an animal forms a social bond with another organism shortly after birth
or hatching.
How are traits inherited?

Gregor Mendel was an Austrian monk who studied and discovered the basic principles of
heredity.

In 1856, Mendel began experimenting with garden pea plants.

He crossed plants that had different traits and observed how those traits were passed on.

Mendel conducted experiments for 7 years.

Mendel determined that inherited traits are passed from parents to offspring during
reproduction.

He believed that each inherited trait is controlled by 2 factors.
o
The offspring receive 1 of these factors from each parent.

Genes (see vocab) are stored on cell structures called chromosomes, which are found in the
nucleus of the cell.

Mendel concluded that for every trait there is a dominant and recessive form.

Each form of the trait can be represented by letters.
o
A capital letter (P) is used for the dominant form of the trait.
o
A lowercase letter (p) is used for the recessive form of the trait.

Mendel’s findings are important because they apply to all organisms.

Dominant traits tend to be expressed more frequently than recessive traits.

Recessive traits are masked by the dominant forms.
How do we trace inherited traits?

Some traits controlled by genes are easy to see, others you cannot see.

A pedigree (see vocab) is used to study heredity patterns.

Parents and offspring are shown in a pedigree.

Horizontal lines connect parents; Vertical lines connect parent to offspring.

Males are represented by boxes; Females are circles.

Dominant traits are shaded; Recessive traits are not shaded.