Download What Is Heredity?

Name
Date
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Assess Your Understanding
What Is Heredity?
What Did Mendel Observe?
1a. DEFINE What happens during fertilization?
b. COMPARE AND CONTRAST In Mendel's cross for stem height, how
did the plants in the F2 generations differ from the F, plants?
gotit?
O I get it! Now I know that Mendel found that one form of a trait
O I need extra help with
How Do Alleles Affect Inheritance?
2a. relate CAUSE AND EFFECT Why is a pea plant that is a hybrid for stem
height tall?
b. (CHALLENGE Can a short pea plant be a hybrid for the trait of stem
height? Why or why not?
gotit?
O I get it! Now I know that an organism's traits are controlled by
O I need extra help with
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79B
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Enrich
What Is Heredity?
When an organism has a trait controlled by a dominant allele, it can either be a hybrid
or a purebred. To find out which, geneticists use a test cross. Read the passage and study
the diagram below. Then use a separate sheet of paper to answer the questions that
follow the diagram.
The Test Cross
In a test cross, the organism with the trait controlled by a dominant allele is crossed with an organism
with a trait controlled by a recessive allele. If all offspring have the trait controlled by the dominant allele,
then the parent is probably a purebred. If any offspring has the recessive strait, then the dominant parent
is a hybrid.
Test Cross
H = Short hair
h = Long hair
W-^u^W^-M,'^^.
P Generation
X
H_?
I
Ft Generation
H
H
1. Is the long-haired cat in the P generation a hybrid or a purebred?
Explain your answer.
2. Is the short-haired cat in the P generation a hybrid or a purebred?
Explain your answer.
3. If the short-haired cat in the P generation were purebred, what
would you expect the offspring to look like?
4. In horses, the allele for a black coat (B) is dominant over the allele for
a brown coat Ob). A cross between a black horse and a brown horse
produces a brown foal. Is the black horse a hybrid or a purebred?
Explain.
5. In guinea pigs, the allele for a smooth coat (5) is dominant over the
allele for a rough coat (s). Explain how you could find out whether a
guinea pig with a smooth coat is a hybrid or a purebred.
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* 79E
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Review and Reinforce
What is Heredity?
Understanding Main Ideas
Study the diagram below. Then use a separate sheet of paper to answer the questions
below the diagram.
P Generation
F1 Generation
F2 Generation
r
~
r
Mf X ^
1. What trait in pea plants is being studied in the cross shown above?
2. What are the two alleles for this trait?
3. Which allele is the dominant allele? Explain how you know.
4. Which allele is the recessive allele? Explain how you know.
5. What alleles do the F, offspring have? Explain which allele was
inherited from each parent.
Building Vocabulary
Match each term with its definition by writing the letter of the correct definition in the
right column on the line beside the term in the left column.
6.
genetics
a. the passing of traits from parents to offspring
7.
allele
b. an organism with two different alleles for a trait
8.
trait
c. a factor that controls traits
9.
dominant allele
d. a physical characteristics of organisms
e. an allele whose trait always shows up in the organism
10.
gene
11.
hybrid
12.
heredity
13.
recessive allele
f. each different form of a gene
g. the scientific study of heredity
h. an allele whose trait is hidden in the presence of a
dominant allele
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79D
Date
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Lesson Quiz
What Is Heredity?
If the statement is true, write true. If the statement is false, change the underlined word
or words to make the statement true.
1.
2.
The scientific study of heredity is called fertilization.
A hybrid organism is the offspring of many generations that
have the same form of a trait.
3.
Capital letters are used to represent recessive alleles.
4.
Mendel called an individual that has one dominant allele and
one recessive allele for a trait a purebred.
5.
Mendel said that the factors that control a trait exist in pairs.
6.
lendel's experiments showed that the traits of an offspring
were not a blend of the characteristics of the parents.
Write the letter of the correct answer on the line at the left.
7. What Mendel called factors are now
called
8. When parent plants are crossed,
scientists refer to the first generation of
A heredity
B genes
offspring as
A P
C purebreds
B F2
D traits
C 1F
D F,
9. A seed can be round or wrinkled.
Seed shape is
10. The allele for a hybrid tall pea plant is
A a trait
represented as
A 77
B an allele
B Tt
C a factor
C T5
D a gene
D tt
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79F