Download Lesson 2 | Understanding Inheritance

Lesson 2 | Understanding Inheritance
Student Labs and Activities
Page
Appropriate For:
Launch Lab
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Content Vocabulary ELL
27
all students
Lesson Outline ELL
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MiniLab
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all students
Content Practice A
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AL
AL
AL
Content Practice B
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AL
OL
BL
Language Arts Support
33
all students
School to Home
35
all students
Key Concept Builders
36
Enrichment
40
Challenge
41
Skill Practice
42
AL
AL
AL
all students
AL
AL
BL
all students
Assessment
Lesson Quiz A
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AL
AL
AL
Lesson Quiz B
44
AL
OL
BL
Teacher Support
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Answers (with Lesson Outlines)
AL Approaching Level
T4
OL On Level
BL Beyond Level
ELL English-Language Learner
Teacher evaluation will determine which activities to use or modify to meet any ELL student’s proficiency level.
Genetics
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Name
Date
Launch Lab
Class
LESSON 2: 15 minutes
What is the span of your hand?
Mendel discovered that some traits have a simple pattern of inheritance—dominant or
recessive. However, some traits, such as eye color, have more variation. Is human hand span
a Mendelian trait?
Procedure
1. Read and complete a lab safety form.
2. Use a metric ruler to measure the
distance (in cm) between the tips of
your thumb and little finger with your
hand stretched out. Record your
measurement below.
3. As a class, record everyone’s name and
hand span in a data table.
Data and Observations
1. What range of hand span measurements did you observe?
2.
Key Concept Do you think hand span is a simple Mendelian trait like pea plant
flower color?
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Think About This
Name
Date
Content Vocabulary
Class
LESSON 2
Understanding Inheritance
Directions: Answer each question or respond to each statement on the lines provided. Use complete sentences.
1. What is the difference between a phenotype and a genotype?
2. What does the term conclude mean?
3. Describe the difference between a homozygous genotype and a heterozygous
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
genotype.
4. How does incomplete dominance differ from codominance?
5. What is the relationship between an allele and a gene?
6. What is the purpose of a Punnett square?
7. Give an example of a trait that is passed through polygenic inheritance.
Genetics
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Name
Date
Class
Lesson Outline
LESSON 2
Understanding Inheritance
A. What controls traits?
1. Inside each cell is a nucleus that contains threadlike structures
called
.
2. Mendel’s factors are parts of chromosomes, and each cell in the offspring contains
chromosomes from both
.
3. A(n)
is a section on a chromosome that has genetic
information for one trait.
4. The different forms of a gene are called
.
5. Geneticists refer to how a trait appears, or is expressed, as the
trait’s
.
6. The two alleles that control the phenotype of a trait are called the
trait’s
.
a. In genetics,
letters represent dominant alleles, and
letters represent recessive alleles.
.
c. If two alleles of a gene are different, its genotype is
.
B. Modeling Inheritance
1. In a situation based on chance, such as flipping a coin, the chance of getting
a certain outcome can be represented by a(n)
as 50:50, or 1:1.
such
2. A(n)
is a model that is used to predict possible
genotypes and phenotypes of offspring.
a. To create a Punnett square, you need to know the
of both parents.
b. If you count large numbers of
from a particular cross,
the overall ratio will be close to the ratio predicted by a Punnett square.
3. A(n)
is a diagram that shows phenotypes of genetically
related family members. It also gives clues about their
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.
Genetics
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b. When two alleles of a gene are the same, its genotype is
Name
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Class
Lesson Outline continued
C. Complex Patterns of Inheritance
1. Alleles show
when the offspring’s phenotype is a blend
of the parents’ phenotypes.
2. Alleles show
when both alleles can be observed in a
phenotype.
3. Unlike the genes in Mendel’s pea plants, some genes have
alleles.
4. ABO
type is a trait that is determined by multiple
alleles.
5.
occurs when multiple genes determine the phenotype
of a trait.
6. Human eye
is an example of polygenic inheritance.
D. Genes and the Environment
1.
are not the only factors that can affect phenotypes.
An organism’s
can also affect its phenotype.
2. The flower color of one type of hydrangea is determined by the
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
in which the hydrangea grows.
3.
Genetics
choices can affect a person’s phenotype.
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Name
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MiniLab
Class
LESSON 2: 20 minutes
Can you infer genotype?
If you know that dragon traits are either dominant or recessive, can you use phenotypes
of traits to infer genotypes?
Procedure
1. Select one trait card from each of
three dragon trait bags. Record the
data in your Science Journal.
2. Draw a picture of your dragon based on
your data. Label each trait homozygous
or heterozygous.
3. For each of the three traits, place one
Dragon Traits
Phenotype Homozygous Heterozygous
Green body
Red body
Four legs
check mark in the appropriate box.
4. Combine your data with your
classmates’ data.
Two legs
Long wings
Short wings
Analyze and Conclude
2. Determine which trait is dominant and which is recessive. Support your reasoning.
3. Determine the genotype(s) for each phenotype. Support your reasoning.
4.
Key Concept Decide whether you could have correctly determined your dragon’s
genotype without data from other dragons. Support your reasoning.
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Genetics
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1. Describe any patterns you find in the data table.
Name
Date
Class
Content Practice A
LESSON 2
Understanding Inheritance
Directions: On the line before each definition, write the letter of the term that matches it correctly. Each
term is used only once.
1. threadlike structures in cells
A. dominance
2. contain instructions for traits
B. pedigree
3. two different forms of a gene
C. genotype
4. outward appearance
D. heterozygous
E. chromosomes
5. determines outward appearance
F. codominance
6. represented by uppercase letters
G. homozygous
7. represented by lowercase letters
H. incomplete dominance
8. RR
I. genes
9. Rr
J. environmental factors
10. shows possible outcomes of genetic crosses
11. shows inherited traits in a family
K. alleles
L. multiple alleles
M. recessiveness
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12. produces a blend of the parents’ phenotypes
N. polygenic inheritance
13. when both alleles are expressed
O. Punnett square
14. determines human blood type
P. phenotype
15. when multiple genes determine a phenotype
16. can sometimes influence expression of genes
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Content Practice B
LESSON 2
Understanding Inheritance
Directions: On the line before each statement, write the letter of the correct answer.
1. Segments of chromosomes that contain coded information for an organism’s
traits are called
A. cells.
B. genes.
C. alleles.
D. genotypes.
2. The outward expression, or appearance, of a genetic trait is its
A. allele.
B. pedigree.
C. phenotype.
D. inheritance.
3. The designation Rr for a pea-plant’s peas shows that the plant is
A. purple.
B. a hybrid.
C. homozygous.
D. a true-breeding plant.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
4. A model that is used to show possible outcomes of cross-breeding is a
A. ratio.
B. coin toss.
C. pedigree.
D. Punnett square.
5. A cow with red hairs and white hairs in its coat is an example of
A. codominance.
B. multiple alleles.
C. polygenic inheritance.
D. incomplete dominance.
6. Variations in people’s height and eye color are due to
A. codominance.
B. multiple alleles.
C. polygenic inheritance.
D. incomplete dominance.
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Language Arts Support
Class
LESSON 2
Reader’s Theater
An Interview with Gregor Mendel
CHARACTERS: Reporter, Gregor Mendel
Reporter: Good evening. Tonight we have a special guest in our studio. His name is Gregor
Mendel. Mr. Mendel was an Austrian friar and a scientific researcher more than 150 years
ago. He traveled in a time machine to get to our interview today. Thank you for coming.
Gregor Mendel: It was a long journey, but I’m glad to be here.
Reporter: Our viewers are interested to hear about how your study of peas changed the
way we view heredity.
Gregor Mendel: I’m glad to hear that my work is important. I started my research in the
1850s.
Reporter: I have some questions I’d like to ask you, if you don’t mind.
Gregor Mendel: No, I don’t mind. Ask any question you’d like.
Reporter: My first question concerns your choice of plants. Why did you use pea plants?
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Gregor Mendel: Pea plants grow and reproduce quickly, so I was able to breed many plants
in a short period of time. Also, they have a wide variety of traits, or characteristics, so I was
easily able to record the results of the cross-pollination of different varieties. I studied many
generations of pea plants to reach my conclusions. My colleagues at the monastery used to
grumble because we ate so many peas.
Reporter: Now I understand why you used peas. Can you describe cross-pollination?
Gregor Mendel: I transferred pollen from the flowers on certain plants to the flowers on
other plants. For example, I transferred pollen from short-stemmed pea plants to other
short-stemmed pea plants. I noted that the offspring from this combination were always
short-stemmed, just like the parents. When I crossed tall-stemmed plants with other tallstemmed plants, however, I noted that tall and short plants grew. To me, this meant that
the short-stemmed trait must be present somewhere in the genetic makeup of the tallstemmed pea plants.
Reporter: And for those of us who don’t have a background in genetics, what did you
conclude from your experiments?
Gregor Mendel: I determined that each parent pea plant must contain two characteristics
for a particular trait. When two plants with different traits, such as tall and short stems,
were bred, the offspring showed only one of the traits. This was then called the dominant
trait, and the trait that did not appear was called recessive.
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Class
Reader’s Theater continued
Reporter: How do you think the traits are inherited?
Gregor Mendel: From the evidence I gathered in my research, I concluded that each parent
contributes one factor to the plant in the offspring generation. So, the offspring in the first
filial generation gets one factor from the female parent and one factor from the male
parent. The two factors interact to produce the resulting trait.
Reporter: Why is this called the study of heredity? What was it about your experiments
that changed the way we look at heredity today?
Gregor Mendel: Until the time I conducted my research, people believed that the blending
of traits resulted when two complex life-forms such as plants reproduced. I disproved that
hypothesis by crossing two different flower colors, for example. I never saw a mixture of
purplish-white flowers on a plant. The result was always purple or white.
Reporter: Can you give us an example with humans?
Gregor Mendel: Sure. Some people have unattached earlobes; that is, a part of the lobe
hangs down from the side of the head. This is a dominant trait. The recessive trait is an
attached earlobe. The lower part of this type of earlobe attaches directly to the side of the
head. If a person’s mother has attached earlobes and the father has unattached earlobes,
then the person will have attached or unattached earlobes, but not something in between.
Not all traits follow such simple patterns of inheritance, but some do.
Reporter: Well, we hope you are aware that your work is important to the scientific
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community, although not everyone recognized your findings during your time. By 1900
your work was recognized as important to the world of biology, specifically to the study of
genetics. Thanks again for your time this evening. We are fortunate to have had this
opportunity to speak with you, Mr. Mendel. Have a pleasant trip back through history.
Name
Date
School to Home
Class
LESSON 2
Understanding Inheritance
For this activity, you will need the tables below and a pencil. Refer to your textbook as needed.
A farmer who raises vegetables wants to cross two types of corn plants. One type is a
homozygous plant with red kernels (RR) and the other is a homozygous plant with white
kernels (rr). For these plants, red color is dominant and white color is recessive. Fill in the
Punnett square below to predict the offspring the farmer should expect.
1. Using the Punnett square, predict the color of the corn kernels. Will the plants produce
all red kernels, all white kernels, or a mixture of both colors?
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2. What would be the ratio of red corn to white corn in the offspring?
Next, the farmer cross-pollinates the red hybrid (Rr) offspring. Complete the Punnett
square below for this cross.
3. Using the Punnett square, predict the color of the corn kernels. Will the plants produce
all red kernels, all white kernels, or a mixture of both colors?
4. What would be the ratio of plants with red kernels to plants with white kernels
in the offspring?
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Class
Key Concept Builder
LESSON 2
Understanding Inheritance
Key Concept What determines the expression of traits?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms
may be used more than once.
alleles
chromosomes
dominant
genes
heterozygous
homozygous
phenotype
recessive
1. An organism’s
genotype
are located on threadlike structures
called
.
2. The different forms of
are called
3. A trait’s
.
is its observable expression in the organism.
4. The observable expression of a trait is determined by its
5. When an organism has two
for a certain trait that are the
of that trait is said to
.
6. When the two
are different, the
is said to be
7. The
.
genotype Rr results in a round pea, because the round
pea allele is
to the wrinkled pea allele.
8. The wrinkled pea phenotype is
and has the
genotype rr.
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Genetics
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same, the
be
.
Name
Date
Key Concept Builder
Class
LESSON 2
Understanding Inheritance
Key Concept What determines the expression of traits?
Directions: The ozmox is a fictional creature with a variety of traits. Study the list of ozmox alleles for the seven
traits below. Then look at the genotypes of a particular ozmox named Glork. Using that information, write Glork’s
phenotype for each trait on the lines provided.
Ozmox alleles:
Hair—shaggy (S); short-haired (s)
Nose—orange (O); green (o)
Tail—long (L); stubby (l)
Teeth—pointed (P); rounded (p)
Claws—curved (C); straight (c)
Eyes—red (R); blue (r)
Ears—big (B); small (b)
Glork’s genotypes: Ss, oo, LL, Pp, cc, rr, BB
1. Hair:
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2. Nose:
3. Tail:
4. Teeth:
5. Claws:
6. Eyes:
7. Ears:
Genetics
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Class
Key Concept Builder
LESSON 2
Understanding Inheritance
Key Concept How can inheritance be modeled?
A Punnett square is a model used to predict the possible outcomes of genetic crosses
between organisms when their genotypes are known.
Directions: Complete the Punnett squares below.
1. Show a first-generation cross between two
true-breeding pea plants—one with purple
flowers (genotype PP) and one with white
flowers (genotype pp).
P
P
P
p
p
p
2. Show a second-generation (hybrid) cross
between two of the plants from the
first-generation cross.
p
Directions: Answer each question on the lines provided.
3. What percentage of the offspring from the first-generation cross is likely to have purple
flowers? White flowers?
4. What percentage of the offspring from the second-generation cross is likely to have
purple flowers? White flowers?
5. What is the chance, in the form of a ratio, that the offspring from the secondgeneration cross have purple flowers?
6. What is a pedigree?
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p
Name
Date
Class
Key Concept Builder
LESSON 2
Understanding Inheritance
Key Concept How do some patterns of inheritance differ from Mendel’s model?
Directions: Complete this spider map with information about the four kinds of complex patterns of inheritance
discussed in the lesson. On each top line, list one of the patterns. On each bottom line, give an example of a trait
produced by that type of inheritance.
1.
2.
Complex
Patterns of
Inheritance
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3.
4.
Directions: Answer each question on the lines provided.
5. What are three environmental factors that can influence plant phenotypes?
6. What causes a Siamese cat to have dark fur on some parts of its body?
7. Which factor determines the wing pattern and coloration of the map butterfly?
Genetics
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Enrichment
Class
LESSON 2
GM Crops
In Colorado, the potato beetle plagued
potato crops for years. Potato beetles
would eat an entire field, leaving nothing
but stems.
In the past, farmers used chemical
pesticides to control the beetle. But
pesticides can contaminate soil and water.
Some pesticides are linked to cancer.
Farmers were left with a difficult choice—
use chemicals that could potentially pollute
the land or let the beetle destroy the potato
crop.
Fortunately, scientists gave farmers a
third option—a “smarter” potato that could
fend off the beetle on its own.
Gene Modification
Concerns over GM Crops
GM crops hold much promise for
reducing malnutrition and starvation.
However, their use raises several concerns.
The genes of GM plants might cross-fertilize
with wild plants and create “superweeds.”
These superweeds could become resistant to
herbicides and compete with food crops for
limited space. In addition, pests targeted by
disease-resistant GM crops might mutate
and become even more difficult to control.
There are also concerns for human
safety. Opponents fear that allergies and
other illnesses could result from eating GM
crops. They point out that scientists likely
do not know all the potential effects of
these crops on humans and the
environment. Already, studies indicate that
the pollen from one variety of GM corn
kills the caterpillar Danaus plexippus, the
larva of the monarch butterfly.
Applying Critical-Thinking Skills
Directions: Answer each question.
1. Summarize What problems prompted scientists to begin developing GM crops?
2. Evaluate Do you think the use of GM crops should be expanded? Why?
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Genetics
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Researchers developed the diseaseresistant potato using gene modification.
Gene modification is a type of
biotechnology that is used to improve
plants, animals, and microorganisms. In
the case of the potato, researchers inserted
a gene that changed the DNA of the
potato. The potato now contains an
organic pesticide, or biopesticide, that is
deadly to the beetle.
Approximately 56 million hectares of
American farmland are planted with
genetically modified (GM) crops. Use of the
technology is increasing in certain Asian,
African, and Latin American countries
where hunger and malnutrition are
epidemic. Scientists are focusing on
developing GM crops that are more
nutritious and more disease-resistant. For
example, researchers have developed a rice
plant that contains iron and vitamin A,
and a genetically altered sweet potato that
resists a destructive virus.
Name
Date
Class
Challenge
LESSON 2
Analyze a Punnett Square for Two Traits
In peas, round shape (R) is dominant over wrinkled shape (r), and yellow color (Y) is
dominant over green (y). Suppose that a pea plant that has genotype RrYy is crossed with
a pea plant that has genotype rrYy. Fill in the Punnett square below to predict the possible
phenotypes and genotypes of the offspring. Then analyze the Punnett square. How
many different phenotypes and genotypes are possible?
RY
Ry
rY
ry
rY
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ry
rY
ry
Genetics
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Skill Practice
Class
Model
LESSON 2: 25 minutes
How can you use Punnett squares to model inheritance?
Geneticists use models to explain how traits are inherited from one generation to the next.
A simple model of Mendelian inheritance is a Punnett square. A Punnett square is a model
of reproduction between two parents and the possible genotypes and phenotypes of the
resulting offspring. It also models the probability that each genotype will occur.
Learn It
In science, a model is a representation of how something in the natural world works.
A model is used to explain or predict a natural process. Maps, diagrams, three-dimensional
representations, and mathematical formulas can be used to help model nature.
Try It
C
1. Use the Punnett square on this page to complete a
cross between a fruit fly with straight wings (cc) and
a fruit fly with curly wings (CC).
2. According to your Punnett square, which genotypes
c
C
Cc
are possible in the offspring?
3. Using the information in your Punnett square,
c
Apply It
4. Based on the information in your Punnett square, how many offspring will have curly
wings? Straight wings?
5. If you switch the locations of the parent genotypes around the Punnett square, does it
affect the potential genotypes of their offspring? Explain.
6.
Key Concept Design and complete a Punnett square to model a cross between
two fruit flies that are heterozygous for curly wings (Cc). What are the phenotypic
ratios of the offspring?
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Genetics
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calculate the ratio of the dominant phenotype
to the recessive phenotype in the offspring.