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Warm-Up Inheritance Patterns

Lesson Question

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WK2 Words to Know

Write the letter of the definition next to the matching word as you work through the lesson. You may use the glossary to help you.

multiple alleles

codominance

polygenic

incomplete dominance

A. an inheritance pattern in which a trait is controlled by many genes

B. an inheritance pattern in which neither allele is dominant and the offspring demonstrate an intermediate form of the alleles from the parents

C. three or more different forms of a gene for a single trait

D. an inheritance pattern in which the alleles are neither recessive nor dominant, and both alleles are expressed in the offspring

Lesson Goals

Explore the different ways traits are inherited.

Examine multiple alleles and polygenic inheritance, and give examples of each.

Differentiate between

dominance.

and incomplete

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Warm-Up Inheritance Patterns

Inheritance of a Trait Affected by a Single Gene

• A allele masks the of the recessive allele.

• The allele for seeds (Y ) in peas is dominant.

• A allele is masked when the dominant allele is present.

• The allele for seeds (y) in peas is recessive.

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Inheritance PatternsInstruction

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Incomplete Dominance

Incomplete dominance is an pattern in which neither allele

is dominant, and the demonstrate an intermediate form of the

alleles from the .

• Red is neither nor .

• is neither dominant nor recessive.

• Pink is the .

Codominance

Codominance is an inheritance in which the are

neither recessive nor dominant, and both alleles are expressed in the offspring.

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Inheritance PatternsInstruction

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Codominance

• Purple is neither dominant nor recessive.

• is neither dominant nor recessive.

• Purple and white are in the .

Multiple Alleles

• Traits controlled by multiple alleles have three or more

different forms of a .

• Example: In the human population, there are four main blood types.

• The four blood types are determined by alleles.

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Inheritance PatternsInstruction

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Alleles Affecting Blood Type

• There are three alleles that affect blood type: IA, IB, and i.

• IA is over i.

• IB is dominant over i.

• i is .

• IA and IB are .

Blood Type Allele Combinations

IAIA or IAi

B IBIB or IBi

IAIB

O ii

Polygenic Inheritance Pattern

Polygenic is an inheritance pattern in which a is controlled by many genes.

Birth of calves of corn ears

Polygenic Traits

When traits are affected by many genes, many are observed.

• Eye color

• color

• Hair color

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Summary Inheritance Patterns

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Answer

Review: Key Concepts

Inheritance Pattern Definition Example(s)

The alleles are neither recessive nor dominant, and both alleles are expressed in

the .

• Speckled chickens

• Two-colored flowers

Incomplete dominance

Neither allele is dominant, and the offspring demonstrate an intermediate form of the alleles from the parents.

• Pink snapdragons

• Palomino horses

alleles

Three or more different forms of a gene exist for a single trait.

• Blood type

PolygenicTraits are affected by

genes.

• Eye, skin, and hair color

• Birth weight

Lesson Question What are some different ways traits are inherited?

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Summary Inheritance Patterns

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