TE Gregor Mendel and
Genetics
Jean Brainard, Ph.D. (JBrainard)
CK12 Editor
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Jean Brainard, Ph.D. (JBrainard)
CK12 Editor
EDITOR
Douglas
(DWilkin)
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Printed: November 26, 2013
Wilkin,
Ph.D.
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Chapter 1. TE Gregor Mendel and Genetics
C HAPTER
1
TE Gregor Mendel and
Genetics
C HAPTER O UTLINE
1.1
Mendel’s Investigations
1.2
Mendelian Inheritance
1.3
Worksheet Answer Keys
(Opening image courtesy of Rasbak, http://commons.wikimedia.org/wiki/File:Blauwschokker_Kapucijner_rijserwt
_bloem_Pisum_sativum.jpg, and under the license of GNU-FDL 1.2.)
Gregor Mendel and Genetics
Outline
Lesson 6.1: Mendel’s Investigations
6.1.1 Mendel and His Pea Plants
• Blending Theory of Inheritance
• Why Study Pea Plants?
• Controlling Pollination
6.1.2 Mendel’s First Set of Experiments
• F1 and F2 Generations
• Law of Segregation
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6.1.3 Mendel’s Second Set of Experiments
• F1 and F2 Generations
• Law of Independent Assortment
6.1.4 Mendel’s Laws and Genetics
• Rediscovering Mendel’s Work
• Genetics of Inheritance
• Genotype and Phenotype
Lesson 6.2: Mendelian Inheritance
6.2.1 Probability
6.2.2 Probability and Inheritance
• Probability and Gamete Formation
• Probability and Fertilization
6.2.3 Using a Punnett Square
•
•
•
•
Predicting Offspring Genotypes
Predicting Offspring Phenotypes
Determining Missing Genotypes
Punnett Square for Two Characteristics
6.2.4 How Mendel Worked Backward to Get Ahead
6.2.5 Non-Mendelian Inheritance
• Codominance and Incomplete Dominance
– Codominance
– Incomplete Dominance
• Multiple Alleles
• Polygenic Characteristics
• Effects of Environment on Phenotype
Pacing the Lesson
Use the Class Periods per Lesson table below as a guide for the time required to teach the lessons of this chapter.
TABLE 1.1:
Lesson
6.1 Mendel’s Investigations
6.2 Mendelian Inheritance
• Class periods are assumed to be 60 minutes long.
2
Number of Class Periods
2.5
2.5
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Chapter 1. TE Gregor Mendel and Genetics
Online Resources
See the following Web sites for appropriate laboratory activities. They allow students to simulate Mendel’s experiments. (Lesson 6.1)
• http://www2.edc.org/weblabs/Mendel/MendelMenu.html
• http://www.accessexcellence.org/AE/AEC/AEF/1996/nolin_pea.php
This Web site has links to information, activities, and videos about Mendel and genetics:
• http://www.kumc.edu/gec/
Students can learn about Mendelian inheritance with this fun activity:
• http://serendip.brynmawr.edu/sci_edu/waldron/#dragon1
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1.1. Mendel’s Investigations
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1.1 Mendel’s Investigations
Key Concept
Gregor Mendel experimented with pea plants to study heredity. Based on his research, he developed his laws of
segregation and independent assortment. Mendel’s laws were rediscovered in 1900 and are now understood in terms
of genes and alleles.
Standards
•
•
•
•
CA.9–12.IE.1.d, k; CA.9–12.LS.2.a, d, e; CA.9–12.LS.3.b
NSES.9–12.A.1.6; NSES.9–12.A.2.1, 6; NSES.9–12.C.3.1; NSES9–12.G.1.1; NSES.9–12.G.3.2, 3, 4
AAAS.9–12.1.A.2; AAAS.9–12.1.B.3, 7; AAAS.9–12.5.B.2; AAAS.9–12.5.F.5; AAAS.9–12.10.H.5
McREL.9–12.11.3.1, 2, 3, 4, 5; McREL.9–12.12.5.5; McREL.9–12.12.6.1, 3; McREL.9–12.12.7.3; McREL.9–12.13.2.1,
5; McREL.9–12.13.3.5
Lesson Objectives
•
•
•
•
Explain why and how Mendel studied pea plants.
Describe the results of Mendel’s experiments.
State Mendel’s laws of segregation and independent assortment.
Outline the genetics of inheritance.
Lesson Vocabulary
• allele: one of two or more different versions of the same gene
• dominant allele: allele that masks the presence of another allele for the same gene when they occur together
in a heterozygote
• genetics: the science of heredity
• genotype: alleles an individual inherits at a particular genetic locus
• heterozygote: organism that inherits two different alleles for a given gene
• homozygote: organism that inherits two alleles of the same type for a given gene
• hybrid: offspring that results from a cross between two different types of parents
• law of independent assortment: Mendel’s second law stating that factors controlling different characteristics
are inherited independently of each other
• law of segregation: Mendel’s first law stating that the two factors controlling a characteristics separate and
go to different gametes
• locus: position of a gene on a chromosome
• phenotype: characteristics of an organism that depend on how the organism’s genotype is expressed
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Chapter 1. TE Gregor Mendel and Genetics
• pollen: tiny grains that bear the male gametes of seed plants and transfer sperm to female reproductive
structures
• pollination: fertilization in plants in which pollen is transferred to female gametes in an ovary
• recessive allele: allele that is masked by the presence of another allele for the same gene when they occur
together in a heterozygote
Teaching Strategies
Check Your Understanding
Ask students to describe the two ways chromosomes/chromatids separate during meiosis. You may want to do a
quick review of meiosis from the chapter The Cell Cycle, Mitosis, and Meiosis.
Introducing the Lesson
Students are likely to have learned about Gregor Mendel in earlier science classes. Call on volunteers to state
anything they already know about Mendel or his work. Record their statements on the board. Tell the class to check
whether the statements are correct when they read this lesson about Mendel’s discoveries.
Activity
Have groups of students create simple models of at least two pairs of homologous chromosomes. (For example,
students might use small strips of paper in different lengths to represent different pairs of chromosomes and paper
of different colors to distinguish members of each pair.) Then have them use their models to simulate segregation
and independent assortment.
Differentiated Instruction
This lesson has important vocabulary terms that students will need to understand as they go forward in biology. If
you haven’t already started a word wall, start with this lesson. Post the vocabulary terms and definitions on a wall.
Leave plenty of space around each term. Then have students add sketches, key words, or examples that help convey
the meaning of the terms. ELL, LPR
Enrichment
Have a few students learn more about De Vries, Correns, and Tschermak and the rediscovery of Mendel’s laws. Ask
them to create a Web page, PowerPoint, or other visual presentation to share what they learn.
Science Inquiry
Have students play the game The Princess and the Wrinkled Pea at the URL below. They will solve a genetics
problem in the guise of a game by applying principles of Mendelian inheritance.
• http://biologica.concord.org/webtest1/web_labs_mendels_peas.htm
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1.1. Mendel’s Investigations
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Real-World Connection
Relate Mendelian genetics to the profession of genetics counseling. Explain that genetics counselors advise people
who are concerned about having a child with a genetic disorder. Counselors may use family histories, Mendelian
genetics, and other tools to determine the probability of a child with a particular genotype. Ask interested students
to investigate this important profession and report back to the class on what they learn.
Reinforce and Review
Lesson Worksheets
Copy and distribute the lesson worksheets in the CK-12 Biology Workbook. Ask students to complete the worksheets
alone or in pairs as a review of lesson content.
Review Questions
Have students answer the Review Questions that are listed at the end of the lesson in their FlexBook.
• Sample answers to these questions will be provided upon request. Please send an email to teachersrequests@ck12.org to request sample answers.
Points to Consider
With his first set of experiments, Mendel found that characteristics appear to skip generations. With his second set
of experiments, he found that different characteristics are inherited independently of one another.
• Why would this information be useful? Can you think of a practical application of Mendel’s laws?
– (Answers may vary; encourage a diversity of suggestions.)
• Could Mendel’s laws be used to predict the characteristics of the offspring of a given set of parents? How do
you think this might be done?
– (Students might say you could make a chart like Figure 6.6 and fill in the cells with possible combinations of parental traits.)
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Chapter 1. TE Gregor Mendel and Genetics
1.2 Mendelian Inheritance
Key Concept
Based on probability and knowledge of Mendelian inheritance, a Punnett square can be used to predict the proportions of different genotypes in the offspring of a given set of parents. Mendel didn’t know about genes, but luckily
he studied simple dominant-recessive traits, so he could work backward from phenotypes to determine the pattern
of inheritance. More complex patterns of inheritance include codominance, incomplete dominance, multiple alleles,
multiple genes, and environmental influences on gene expression.
Standards
• CA.9–12.IE.1.a, d, g, j; CA.9–12.LS.2.a, c, d, e, g; CA.9–12.LS.3.a, c
• NSES.9–12.A.1.6; NSES.9–12.A.2.1, 4, 6
• AAAS.9–12.5.B.2; AAAS.9–12.5.F.5; AAAS.9–12.12.B.1
Lesson Objectives
•
•
•
•
•
Define probability.
Explain how probability is related to inheritance.
Describe how to use a Punnett square.
Explain how Mendel interpreted the results of his experiments.
Describe complex patterns of inheritance.
Lesson Vocabulary
• codominance: relationship between two alleles for the same gene in which both alleles are expressed equally
in the phenotype of the heterozygote
• incomplete dominance: relationship between the alleles for a gene in which one allele is only partly dominant
to the other allele so an intermediate phenotype results
• polygenic characteristic: characteristic, or trait, controlled by more than one gene, each of which may have
two or more alleles
• probability: the likelihood, or chance, than a certain event will occur
• Punnett square: chart for determining the expected percentages of different genotypes in the offspring of two
parents
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1.2. Mendelian Inheritance
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Teaching Strategies
Introducing the Lesson
Toss a coin to see if a head or tail turns up, after first asking the class to predict the outcome of the toss. Use the
coin toss as a vehicle to introduce the concept of probability. Tell students they will learn how probability is related
to heredity when they read this lesson.
Activity
Assign the drag-and-drop activity at the URL below. Students will use Punnett squares to determine expected
proportions of genotypes and phenotypes of offspring.
• http://www.zerobio.com/drag_gr11/mono.htm
Differentiated Instruction
Pair ELL and native English speakers, and ask partners to make a cluster diagram for the section “Non-Mendelian
Inheritance.” ELL
Enrichment
Have students who need extra challenges solve the case study Those Old Kentucky Blues at the URL below. In this
honors activity, they will use pedigrees and other information to determine the inheritance pattern of an interesting
genetic condition.
• http://sciencecases.lib.buffalo.edu/cs/collection/detail.asp?case_id=208&id=208
Science Inquiry
Have students use Mendelian principles to solve the genetics problems at the URL below.
• http://www.biology.arizona.edu/mendelian_genetics/problem_sets/monohybrid_cross/monohybrid_cross.html
Overcoming Misconceptions
Students commonly think that the expected proportions of genotypes in offspring, as given in a Punnett square, are
the actual proportions. Explain that they are only the most likely proportions, and other proportions may occur in
any given family.
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Chapter 1. TE Gregor Mendel and Genetics
Reinforce and Review
Lesson Worksheets
Copy and distribute the lesson worksheets in the CK-12 Biology Workbook. Ask students to complete the worksheets
alone or in pairs as a review of lesson content.
Review Questions
Have students answer the Review Questions that are listed at the end of the lesson in their FlexBook.
• Sample answers to these questions will be provided upon request. Please send an email to teachersrequests@ck12.org to request sample answers.
Points to Consider
Like most of the characteristics of living things, the characteristics Mendel studied in pea plants are controlled by
genes. All the cells of an organism contain the same genes, because all organisms begin as a single cell. Most of the
genes code for proteins.
• How is the information encoded in a gene translated into a protein? Where does this occur, and what processes
are involved?
– (Students may or may not be familiar with the processes of protein synthesis — transcription and
translation — and the role of ribosomes in the latter process.)
• If cells have the same genes, how do you think different cells arise in an organism? For example, how did you
come to have different skin, bone, and blood cells if all of your cells contain the same genes?
– (Sample answer: I think that different genes are translated into proteins in different cells.)
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1.3. Worksheet Answer Keys
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1.3 Worksheet Answer Keys
• The worksheet answer keys are available upon request. Please send an email to teachers-requests@ck12.org
to request the worksheet answer keys.
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