Lesson 1 | Mendel and His Peas

Lesson 1 | Mendel and His Peas
Student Labs and Activities
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Appropriate For:
Launch Lab
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Content Vocabulary ELL
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Lesson Outline ELL
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MiniLab
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Content Practice A
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Content Practice B
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Math Skills
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School to Home
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Key Concept Builders
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Enrichment
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Challenge
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Lesson Quiz A
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Lesson Quiz B
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Assessment
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Answers (with Lesson Outlines)
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AL Approaching Level
T2
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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 1: 10 minutes
What makes you unique?
Traits such as eye color have many different types, but some traits have only two types. By
a show of hands, determine how many students in your class have each type of trait below.
Refer to the table in your textbook to see images of these traits.
Student Traits
Trait
Type 1
Type 2
Earlobes
Unattached
Attached
Thumbs
Curved
Straight
Interlacing fingers
Left thumb over right thumb
Right thumb over left thumb
Think About This
1. Why might some students have types of traits that others do not have?
your reasoning.
3.
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Key Concept What do you think determines the types of traits you inherit?
Genetics
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2. If a person has dimples, do you think his or her offspring will have dimples? Explain
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Date
Class
Content Vocabulary
LESSON 1
Mendel and His Peas
Directions: On each line, write the term from the word bank that correctly replaces the underlined words in each
sentence. NOTE: You may need to change a term to its plural form.
dominant trait
egg
genetics
hybrid
recessive trait
sperm
heredity
1. Mendel used his pea plants to study the passing of traits
from parents to offspring.
2. Mendel’s research is considered to be the foundation
of the study of how traits are passed from parent to
offspring.
3. Mendel cross-pollinated pea plants with different forms
of the same trait to produce offspring with two different
forms of the same trait.
4. Mendel concluded that the haploid cell formed in a
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
female reproductive organ contributed one genetic
factor for each trait.
5. The other genetic factor for each trait comes from a
haploid cell formed in the male reproductive system.
6. In some cases, one of the factors, such as purple flower
color, was the factor that blocked the other genetic factor.
7. The other factor was the one that is blocked by the
presence of the dominant factor.
Genetics
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Name
Date
Class
Lesson Outline
LESSON 1
Mendel and His Peas
A. Early Ideas About Heredity
1.
is the passing of traits from parents to offspring.
2. In the 1850s,
, an Austrian friar, performed experiments
that helped answer questions about how traits are inherited.
3.
is the study of how traits pass from parents to
offspring.
B. Mendel’s Experimental Methods
1. Pea plants were ideal for genetic studies because they
quickly; they have easily observed
; and the
experimenter can control which pairs of plants
2. Mendel controlled which plants
.
other plants.
a. When a(n)
plant self-pollinates, it always produces
offspring with traits that match the parent.
b. By
plants himself, Mendel was able to select which
plants pollinated other plants.
in the
.
C. Mendel’s Results
1. Mendel’s crosses between true-breeding plants with purple flowers produced plants
with only
flowers. Crosses between true-breeding plants
with white flowers produced plants with only
flowers.
2. Crosses between true-breeding plants with purple flowers and true-breeding plants
with white flowers produced plants with only
flowers.
3. The first-generation purple-flowering plants are called
plants.
4. When Mendel cross-pollinated two hybrid plants, the trait that had disappeared in
the first generation always
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in the second generation.
Genetics
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3. With each cross-pollination Mendel did, he recorded the traits that appeared
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Lesson Outline continued
5. Mendel analyzed the data from many experiments on seven different
. He always noted a 3:1
;
for example, purple flowers grew from hybrid crosses
times more often than white flowers.
D. Mendel’s Conclusions
1. After analyzing the results of his experiments, Mendel concluded that two
control each trait.
2. Mendel also proposed that, when organisms reproduce, each
, sperm or egg, contributes one factor for each trait.
3. A genetic factor that blocks another genetic factor is
.
4. A genetic factor that is blocked by the presence of a dominant factor is
called
.
5. For the second generation, Mendel cross-pollinated two hybrids with purple
flowers. About
percent of the second-generation plants
had purple flowers. These plants had at least one
factor.
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percent of the second-generation plants had white
flowers. These plants had the same two
Genetics
factors.
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Name
Date
MiniLab
Class
LESSON 1: 20 minutes
Which is the dominant trait?
Imagine you are Gregor Mendel’s lab assistant studying pea plant heredity. Mendel has
crossed true-breeding plants with axial flowers and true-breeding plants with terminal
flowers. Use the data below to determine which trait is dominant.
Pea Flower Location Results
Axial
(Number of Offspring)
Terminal
(Number of Offspring)
First
794
0
Second
651
207
Generation
Analyze and Conclude
1. Determine which trait is dominant and which trait is recessive. Support your answer
with data.
Key Concept Analyze the first-generation data. What evidence do you have that
one trait is dominant over the other?
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Genetics
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2.
Name
Date
Content Practice A
Class
LESSON 1
Mendel and His Peas
Directions: On the line before each statement, write T if the statement is true or F if the statement is false.
1. Genetics is the study of how traits are passed from parents to offspring.
2. Gregor Mendel studied pea plants because they reproduce slowly and have
easily observable traits.
3. Pollination in pea plants can occur in three ways.
4. Mendel began his experiments with pea plants that stayed the same from
one generation to the next.
5. He then crossed those plants to create true-breeding plants.
6. In Mendel’s studies of the colors of purple pea flowers, none of
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
the first-generation crosses had white flowers.
7. In those same experiments, about three-fourths of the second-generation
crosses had white flowers.
8. From those results, Mendel concluded that white flowers on pea plants
are a dominant trait.
9. In other studies, a trait that showed up in the same proportion of
second-generation crosses as white flowers did was yellow pods.
10. One trait that Mendel did not study in pea plants was the shape of the
plants’ leaves.
Genetics
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Name
Date
Class
Content Practice B
LESSON 1
Mendel and His Peas
Directions: Answer each question or respond to each statement on the lines provided.
1. What is genetics?
2. State three reasons why Gregor Mendel chose pea plants for his experiments.
3. What did Mendel produce when he cross-bred different true-breeding plants?
4. When Mendel crossed plants that had always produced only purple flowers with
ones that had always produced only white flowers, what was the outcome of the
first-generation cross?
6. What conclusions did Mendel draw from these results and from experiments with other
pea-plant traits? Describe genetic factors and the principle of dominant/recessive.
14
Genetics
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5. What happened when he crossed those plants to produce a second-generation cross?
Name
Date
Math Skills
Class
LESSON 1
Use Ratios
A ratio is a comparison of two quantities. Imagine you have 15 pens and 3 pencils. The
15
ratio of pens to pencils can be written in three ways: 15 to 3, 15:3, and ___
. Like a fraction,
3
a ratio may be simplified. To simplify the ratio 15:3, divide both terms by the greatest
common factor, 3. So, 15:3 = 5:1.
A cross of two pea plants yields 400 seeds. You count 300 yellow seeds and 100 green
seeds. What is the ratio of green seeds to yellow seeds?
Step 1 Write the ratio.
green:yellow = 100:300
Step 2 Divide by the greatest common factor to simplify.
100 ÷ 100 = 1, and 300 = 100 = 3.
100:300 = 1:3
The ratio of green to yellow seeds is 1:3.
Practice
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1. In a garden plot, you count 50 tall
plants and 50 short plants. All the
plants are offspring of the same two
parent plants. What is the ratio of tall
to short plants?
2. In a garden plot, you count 450
yellow-flowered plants and 1,350
white-flowered plants. All the plants
are offspring of the same two parent
plants. What is the ratio of whiteflowered to yellow-flowered plants?
Genetics
3. In a garden plot, you count 125 redflowered plants and 125 pink-flowered
plants. All the plants are offspring of
the same two parent plants. What is
the ratio of red-flowered to pinkflowered plants?
4. In a container of seeds, you count
35 dark-brown seeds and 105 lightbrown seeds. All the seeds come from a
cross between the same two parents.
What is the ratio of dark-brown seeds
to light-brown seeds?
15
Name
Date
School to Home
Class
LESSON 1
Mendel and His Peas
Directions: Use your textbook to answer each question or respond to each statement.
1. Gregor Mendel is often called the father of genetics.
What is heredity, and how does it relate to genetics?
2. Gregor Mendel proved that the idea of blended inheritance was wrong.
What was the idea of blended inheritance, and how did Mendel prove it wrong?
3. In Mendel’s experiments, true-breeding purple flowering pea plants
What was the result when Mendel cross-pollinated true-breeding purple flowering
plants and true-breeding white flowering plants? Relate this to the idea of blended
inheritance.
4. Mendel cross-pollinated second-generation purple-flowering hybrids.
What was the result of the second-generation cross, and why was it important?
16
Genetics
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were crossed to produce purple flowering offspring. True-breeding white
flowering pea plants were crossed to produce white flowering offspring.
Name
Date
Class
Key Concept Builder
LESSON 1
Mendel and His Peas
Key Concept Why did Mendel conduct cross-pollination experiments?
Directions: On the line before each definition, write the letter of the term that matches it correctly. Each
term is used only once.
1. the passing of traits from parents to offspring
A. self-pollination
2. the study of how traits are passed on
B. pistil
3. when pollen from one plant lands on the pistil
C. pollen carriers
of a flower on the same plant
4. when pollen from one plant reaches the pistil
of a flower on a different plant
D. stamen
E. heredity
F. cross-pollination
5. bees, wind, and water
G. true-breeding plant
6. easily noted characteristics
H. observable traits
7. when offspring are the same as the parent
I. genetics
8. source of pollen
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9. receiver of pollen
Genetics
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Name
Date
Class
Key Concept Builder
LESSON 1
Mendel and His Peas
Key Concept Why did Mendel perform cross-pollination experiments?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Each term
is used only once.
color
cross-breeding
cross-pollination
first
hybrid
length
reproduce
second
self-pollination
traits
true-breeding
1. Gregor Mendel experimented with pea plants because they
quickly and have easily observed
control which plants reproduced.
, and because he could
2. Pollination in pea plants can occur in the following two ways:
or
.
3. Mendel started with
plants—plants with the exact same
characteristics from one generation to the next.
of the flowers and the
of the stems.
5. By
different pea plants, Mendel produced a variety of
plants.
6. He noted that characteristics that were not present in a
-generation cross showed up in about 25 percent of the
plants in a
18
-generation cross.
Genetics
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4. Those characteristics included the
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Date
Class
Key Concept Builder
LESSON 1
Mendel and His Peas
Key Concept What did Mendel conclude about inherited traits?
In his experiments with pea plants, Mendel concluded that some traits are dominant
and others are recessive.
Directions: On the line before each trait, write D if it is dominant or R if it is recessive.
1. white flowers
2. purple flowers
3. yellow seeds
4. green seeds
5. wrinkled seeds
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6. round seeds
7. smooth pods
8. bumpy pods
9. short stems
10. long stems
Directions: On the line before each statement, write T if the statement is true or F if the statement is false.
11. Mendel concluded that each trait he observed was controlled by two factors—
one from the egg cell and the other from the sperm cell.
12. He called them factors because nothing was known about genes in his time.
13. He concluded that a recessive factor always blocks a dominant factor.
Genetics
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Name
Date
Class
Key Concept Builder
LESSON 1
Mendel and His Peas
Key Concept How do dominant and recessive factors interact?
Directions: On the line before each pea-pod cross, write the letter of the most likely outcome.
1. a true-breeding purple-flower plant crossed with a true-breeding white-flower
plant
A. all white-flower plants
B. all purple-flower plants
C. mostly purple-flower plants
2. a cross between two hybrid purple-flower plants (purple and white)
A. all purple flower plants
B. mostly white-flower plants
C. mostly purple-flower plants
3. a hybrid purple-flower plant (purple and white) crossed with a true-breeding
white-flower plant
A. all purple-flower plants
B. mostly purple-flower plants
C. half purple-flower plants and half white-flower plants
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Directions: Answer each question on the lines provided.
4. Why would it have been impossible for Mendel to create heterozygous pea plants
with short stems, green seeds, or bumpy pods?
5. Out of the many hybrid pea plants that Mendel crossed, about what percent of
the second-generation plants had
a. the dominant form of each trait?
b. the recessive form of each trait?
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Genetics
Name
Date
Enrichment
Class
LESSON 1
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Hybrids in the Wild
You have learned about hybrids that are
produced when two parents of different
breeds mate. But did you know that
hybrids are also produced when parents
from closely related species, such as a tiger
and a lion, mate? Sometimes animals
produced by these type of interspecies
hybrids cannot reproduce and might not
be as healthy as purebreds.
Scientist Ben Fitzpatrick studies hybrid
salamanders produced from inter-species
crosses. When he first began his field
studies of the salamanders, he expected the
hybrids to be weaker than the purebred
salamanders. To Fitzpatrick’s surprise, the
wild hybrid salamanders were thriving.
“The level of vigor in these hybrids was
completely unexpected,” he said in an
interview with the journal BioMedicine. The
research might have important implications
for endangered species and the
conservationists who work to save them.
The Study
To understand the implications of
Fitzpatrick’s work, it is necessary to go back
to the 1950s, when fishermen in California
began releasing barred tiger salamanders
into ponds and other bodies of water. The
fisherman used salamanders for bait, and
wanted to increase their bait supplies.
Barred tiger salamanders are nonnative
species. Over time, they interacted and
mated with California tiger salamanders,
a native endangered species.
Fitzpatrick and his colleagues compared
the survival rates of three groups of
salamander offspring: pure barred tiger,
pure California tiger, and hybrids of the
two species. They discovered that the
hybrid offspring had higher rates of
survival than either purebred group.
The scientists do not yet know why the
hybrid offspring are thriving. Regardless,
the study predicts that the hybrids will
contribute to the gene pool of the purebred
salamander species now and in the future.
Helping or Hurting Endangered Species?
The California tiger salamander is an
endangered species. If the study’s prediction
is correct, eventually hybrid genes will be
present in all California tiger salamanders.
The native salamanders will survive. But will
they still be considered a separate species?
The question is important in terms of
managing endangered species. The fate of
the California tiger salamanders might lie
in the hands of conservationists. They
might determine that the species is no
longer genetically pure and that the
hybrids are pushing the native purebreds to
extinction. Or they might decide that the
salamanders with hybrid genes represent an
adaptation of the species, allowing it to
thrive in the wild.
Applying Critical-Thinking Skills
Directions: Answer each question or respond to each statement.
1. Infer Why might the hybrid offspring have higher survival rates than the offspring of
the purebred salamanders?
2. Predict what might happen to conservation efforts for the California tiger salamanders
if they are no longer considered to be genetically pure.
Genetics
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Name
Challenge
Date
Class
LESSON 1
Mendel’s Work on Genetics
Gregor Mendel is often called the father of genetics for his groundbreaking studies
of how traits are passed from parents to offspring. When Mendel was performing his
experiments, most people believed in blending inheritance, the idea that all traits mix
like colors of paint. Mendel’s work disproved this idea.
Create a Skit
In the space below, write a skit about Mendel and his work. In the skit, Mendel should
explain the results of his experiments to a group of skeptical scientists. The skit should have
a setting, characters, and dialogue. Include these terms in the dialogue—egg, sperm, truebreeding, hybrid, dominant, and recessive.
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Genetics