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1. For each pair of terms, explain how the meanings of the terms differ.

a. germ-cell mutation and somatic-cell mutation b. multiple-allele and polygenic c. sex-linked trait and sex-influenced trait d. amniocentesis and chorionic villi sampling

2. Explain the relationship between a chromosome map and a map unit.

3. Use the following terms in the same sentence: point mutation, substitution, and frameshift mutation.

4. Word Roots and Origins The word somatic is derived from the Greek somatikos, which means "body." Using this information, explain why the term somatic-cell mutation is a good name for what the term describes.

Understanding Key Concepts

5. Compare sex chromosomes and autosomes.

6. Identify the evidence that led Morgan to hypothesize that the gene for eye color in Drosophila melanogaster is carried on the X chromosome.

7. Describe where the human SRY gene resides and its significance.

8. Relate how X-linked genes affect the inheritance of sex-linked traits.

9. Evaluate the relationship between crossing over, recombinant types, and chromosome mapping.

10. Differentiate between a chromosome mutation and a point mutation.

11. Differentiate between nondisjunction and translocation mutations.

12. State the type of information that is obtained by analyzing a pedigree.

13. Describe the pattern of inheritance in Huntington's disease.

14. Predict the possible genotypes for a person whose ABO blood group is type A.

15. Summarize two ways in which geneticists can detect genetic disorders.

16. Describe how gene therapy is used to treat genetic disorders.

17. Unit 5—Heredity

¿¡«M^ Write a report summarizing the BML0G9 « latest findings on treating a genetic disorder with gene therapy. What obstacles still need to be overcome?

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CONCEPT MAPPING Use the following terms to create a concept map that describes the ways that changes in DNA occur: mutation, chromosome mutation, substitution, deletion, point mutation, death, inversion, translocation, nondisjunction, germ-cell mutation, lethal mutation, and gametes.

Critical Thinking

19. Analyzing Data In Drosophila the genes for body color and wing length are on the same chromosome. Gray body (G) is dominant to black body (g), and long wings (L) are dominant to short wings (l). Assume that both dominant alleles are on the same chromosome. Draw a Punnett square representing the cross GgLl X GgLl. Write the phenotypic and genotypic ratios that would be expected among the offspring, assuming that crossing-over does not occur.

20. Relating Concepts Individuals who are heterozygous for sickle cell anemia should avoid extreme conditions that severely reduce the amount of oxygen available to the body, such as playing vigorous sports at high elevations. Explain why this would be advisable.

21. Inferring Relationships A 20-year-old man with cystic fibrosis has a sister who is soon to be married. If you were the man, how would you explain your sister's likelihood of having children with cystic fibrosis?

22. Interpreting Graphics The individual shown in blue (third from the left, bottom row) in the pedigree below is affected by a genetic disorder. State the pattern of inheritance for the disorder and whether the disorder is autosomal or sex-linked. Explain your answer.

23. What advice might a genetic counselor give to the unaffected brothers and sister shown in the pedigree in question 22?

Standardized Test Preparation

DIRECTIONS: Choose the letter of the answer choice that best answers the question.

1. Which can a chromosomal map show?

A. the sex of the individual

B. the presence of mutant alleles

C. the positions of genes on a chromosome

D. whether a gene is autosomal or recessive

2. Which can result from the deletion of a single nucleotide?

F. trisomy

G. a translocation

H. nondisjunction

J. a frameshift mutation

3. At the present time amniocentesis cannot reveal which of the following?

A. eye color

B. genetic disease

C. sex of the fetus

D. chromosomal abnormalities

4. A geneticist working with the fruit fly Drosophila melanogaster discovers a mutant phenotype that appears only in males who are offspring of males of the same phenotype. What does this information suggest about the mutant phenotype?

F. The trait is X-linked.

G. The trait is Y-linked.

H. The trait is autosomal dominant. J. The trait is autosomal recessive.

INTERPRETING GRAPHICS: The table below shows the genotypes and phenotypes of pattern baldness. Use the table to answer the question that follows.

Genotypes and Phenotypes of Pattern Baldness

Genotype

Phenotype

Female

Male

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