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Chapter 12
Patterns of Inheritance
BIOLOGY
Thirteenth Edition
Raven, Johnson, Mason, Losos,
Duncan
© 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
, Mystery of heredity
Before the 20th century, two concepts were the basis for
ideas about heredity
• Heredity occurs within species
• Traits are transmitted directly from parent to offspring
© McGraw Hill, LLC 2
, Gregor Mendel
Pea plants were optimal because:
1. Other research showed that
pea hybrids could be
produced
2. Many pea varieties were
available
3. Peas are small plants and
easy to grow
Leslie Holzer/Science Source
4. Peas can self-fertilize or be
cross-fertilized
© McGraw Hill, LLC 3
, Mendel’s experimental method
Usually in three stages
1. Produce true-breeding strains for each trait he was
studying
2. Cross-fertilize true-breeding strains having alternate
forms of a trait
3. Allow the hybrid offspring to self-fertilize for several
generations and count the number of offspring showing
each form of the trait
© McGraw Hill, LLC 4
Chapter 12
Patterns of Inheritance
BIOLOGY
Thirteenth Edition
Raven, Johnson, Mason, Losos,
Duncan
© 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
, Mystery of heredity
Before the 20th century, two concepts were the basis for
ideas about heredity
• Heredity occurs within species
• Traits are transmitted directly from parent to offspring
© McGraw Hill, LLC 2
, Gregor Mendel
Pea plants were optimal because:
1. Other research showed that
pea hybrids could be
produced
2. Many pea varieties were
available
3. Peas are small plants and
easy to grow
Leslie Holzer/Science Source
4. Peas can self-fertilize or be
cross-fertilized
© McGraw Hill, LLC 3
, Mendel’s experimental method
Usually in three stages
1. Produce true-breeding strains for each trait he was
studying
2. Cross-fertilize true-breeding strains having alternate
forms of a trait
3. Allow the hybrid offspring to self-fertilize for several
generations and count the number of offspring showing
each form of the trait
© McGraw Hill, LLC 4
