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Date
Class
Human Genetic Disorders
Inquiry Warm-Up, How Many Chromosomes?
In the Inquiry Warm-Up, you investigated how many chromosomes there are in each cell
of a person who has Down syndrome. Using what you learned from that activity, answer
the questions below.
1. USE PRIOR KNOWLEDGE Why does each human body cell usually
contain an even number of chromosomes?
2. USE PRIOR KNOWLEDGE Why does each human body cell usually
contain chromosomes that are all in pairs?
3. INFER Based on your observations, is Down syndrome caused by a
variation in a single gene or by a variation in the structure or number
of chromosomes?
4. CLASSIFY Think about which chromosome pair is abnormal in a person
with Down syndrome. Is Down syndrome a sex-linked trait? Explain.
Name
Date
Class
Human Genetic Disorders
How Are Genetic Disorders Inherited in Humans?
1a. EXPLAIN Which of the two major causes of genetic disorders is
responsible for Down syndrome?
b. INFER Why is hemophilia more common in males?
I get it! Now I know that the two major causes of genetic disorders are
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How Are Genetic Disorders Traced, Diagnosed, and Treated?
I get it! Now I know that genetic disorders are traced, diagnosed, and treated by
I need extra help with
Name
Date
Class
Human Genetic Disorders
On a separate sheet of paper, describe what cystic fibrosis is and what causes it. Then
explain what a couple planning a family can do if they have a family history of cystic
fibrosis.
Name
Date
Class
Human Genetic Disorders
Understanding Main Ideas
Complete the table below.
Human Genetic Disorders
1.
Disorder
Type of Allele
Cystic fibrosis
Recessive
2.
3.
Codominant
Hemophilia
Effects on Body
Abnormal hemoglobin
Blood clots poorly.
Answer the following questions on a separate sheet of paper.
4. How does a person with one sickle-cell allele differ from a person
with two sickle-cell alleles?
5. Why is hemophilia more common in males than in females?
6. Explain what causes Down syndrome.
Building Vocabulary
Fill in the blank to complete each statement.
7. An abnormal condition that a person inherits through genes or chromosomes is a(n)
.
8. A(n)
is a picture of all the chromosomes in a cell.
9. A chart or family tree that tracks which members of a family have a particular trait is
called a(n)
.
Name
Date
Class
Human Genetic Disorders
Read the passage and study the maps below. Then use a separate sheet of paper to
answer the questions that follow.
Sickle-Cell Allele and Malaria
The allele for sickle-cell disease is most common in people of African ancestry. The reason for this
probably has to do with the relationship between the sickle-cell trait and malaria. Malaria, a disease
common in parts of Africa, affects red blood cells. Carriers of the sickle-cell allele are resistant to malaria.
Scientists think that the sickle-cell trait helps carriers resist malaria. The map on the left shows the
distribution of malaria worldwide today. The map on the right shows the distribution of the sickle-cell
allele.
1. Where is malaria most common today?
2. Where is the sickle-cell allele most frequent?
3. Malaria is caused by a microscopic parasite that infects the blood.
Based on this fact, hypothesize why people with sickle-cell trait are
resistant to malaria. (Hint: A parasite is an organism that lives and
feeds on or in another organism.)
4. Suppose malaria were eliminated as a human disease. Predict how
the frequency of the sickle-cell allele might change over time. Explain
your prediction.
Name
Date
Class
Human Genetic Disorders
Write the letter of the correct answer on the line at the left.
1.
Which of the following is a genetic
disorder that results when two mutated
alleles are inherited?
A Down syndrome
B colorblindness
C cystic fibrosis
D hemophilia
2.
Which of the following is the
protein that is NOT normal in people
with sickle-cell disease?
A mucus
B clotting protein
C karyotype
D hemoglobin
3.
Which of the following is a genetic
disorder that results from having an extra
chromosomes?
A Down syndrome
B colorblindness
C cystic fibrosis
D hemophilia
4.
Which is not a cause of human
genetic disorders?
A changes in the number of chromosomes
B abnormal hemoglobin
C changes in the structure of
chromosomes
D mutations in the DNA of genes
Fill in the blank to complete each statement.
5. To trace the occurrence of a trait through several generations of a family, you could
create a(n)
.
6. A couple that have a family history of a genetic disorder might wish to receive advice
from a(n)
.
7. The allele for the sickle-cell trait is
8.
with the normal allele.
is a genetic disorder caused by a recessive allele on the
X chromosome.
9. A doctor may use a(n)
to examine the chromosomes in a cell.
10. A condition in which a person’s skin, hair, and eyes lack normal coloring is called
.