Section 1: Chromosomes and Phenotype KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits. VOCABULARY carrier sex-linked gene X chromosome inactivation MAIN IDEA: Two copies of each autosomal gene affect phenotype. Fill in the blank or circle the word or phrase that best completes the sentence. 1. Sex chromosomes determine an organism s. All other chromosomes, which do not directly affect an organism s sex, are called. 2. A person who is a carrier differs from a person who has a genetic disorder. A carrier does / does not show symptoms of a disorder but can / cannot pass the disorder to offspring. 3. Complete the two Punnett squares below to compare autosomal recessive disorders with autosomal dominant disorders. Fill in the possible genotypes for offspring, and write in the phenotype (no disorder, carrier, or disorder) for each. Autosomal Recessive Autosomal Dominant D d D d D D d d Holt McDougal Biology 1 Extending Mendelian Genetics Section 1: Chromosomes and Phenotype
continued MAIN IDEA: Males and females can differ in sex-linked traits. 4. Sex-linked genes are located on the. 5. Fill in the Punnett square below to show the pattern of inheritance for sex chromosomes. Write in the phenotype (male or female) for each. Sex Chromosome Inheritance X X X Y Circle the word or phrase that best completes the statement. 6. In humans, a gamete from a male determines the sex of the offspring, because a male can pass on only X / only Y / either X or Y chromosomes. In contrast, a female passes on only X / only Y / either X or Y chromosomes. 7. The genes on the Y chromosome are responsible for male / female characteristics. 8. Place a check mark in the appropriate boxes to show how sex-linked genes are expressed in the phenotypes of males and females. Show phenotypes from all sex-linked genes. Show phenotypes similarly to autosomal gene expression. Males Females Vocabulary Check Circle the word or phrase that best completes the statement. 9. The verb carry means to transport. This meaning is related to the term carrier in genetics, because a carrier is a person who transports a disease-causing allele to offspring / parents. 10. With X chromosome inactivation, which occurs in males / females, one of the two X chromosomes in every cell is randomly turned off / turned up. Holt McDougal Biology 2 Extending Mendelian Genetics Section 1: Chromosomes and Phenotype
Section 2: Complex Patterns of Inheritance KEY CONCEPT Phenotype is affected by many different factors. VOCABULARY incomplete dominance codominance polygenic trait MAIN IDEA: Phenotype can depend on interactions of alleles. 1. Circle the letter of all of the following statements that are true about incomplete dominance. a. Both alleles are completely expressed. b. Neither allele is completely dominant. c. Neither allele is expressed. d. One allele is not hidden in a heterozygote. e. Heterozygous phenotype contains the separate products of both alleles. f. Heterozygous phenotype is somewhere between the homozygous phenotypes. 2. Circle the letter of all of the following statements that are true about codominance. a. Both alleles are completely expressed. b. Neither allele is completely dominant. c. Neither allele is expressed. d. One allele is not hidden in a heterozygote. e. Heterozygous phenotype contains the separate products of both alleles. f. Heterozygous phenotype is somewhere between the homozygous phenotypes. Circle the word or phrase that best completes the statement. 3. With a multiple-allele trait, the gene has less than / only / more than two alleles. Holt McDougal Biology 3 Extending Mendelian Genetics Section 2: Complex Patterns of Inheritance
continued Place the following statements into the appropriate boxes to indicate how phenotypes appear in incomplete dominance and codominance and to provide an example of each. a. A third phenotype that has both of the homozygous parental phenotypes. b. A third, distinct phenotype that has neither of the homozygous parental phenotypes. c. Blood type (one parent has blood type A, one parent has blood type B, offspring has blood type AB). d. The 4 o clock plant (one parent has red flowers, one parent has white flowers, offspring has pink flowers). Interaction Phenotype Example Incomplete dominance 4. 5. Codominance 6. 7. MAIN IDEA: Many genes may interact to produce one trait. Fill in the blank with the word or phrase that best completes the sentence. 8. Polygenic traits are produced by two or more and show a continuous range of. One example is eye color. 9. Epistasis is the term for one gene affecting the of other genes involved in a particular trait. One example is albinism. MAIN IDEA: The environment interacts with genotype. 10. Genotype is not the only factor that affects phenotype. The can affect gene expression, which will influence phenotype. 11. Complete the following sentences, which give examples of how environment and genotype can interact. In sea turtles, sex determination depends on both genes and the at which sea turtle eggs mature. In humans, height is affected by both genes and factors such as. Holt McDougal Biology 4 Extending Mendelian Genetics Section 2: Complex Patterns of Inheritance
continued Vocabulary Check Fill in the blank with the word or phrase that best completes the sentence. 12. The prefix in- means not. In genetics, the term means that neither allele is dominant. 13. The prefix co- means together. In genetics, the term means that both alleles are expressed together. 14. The prefix poly- means many, and the term genic means related to genes. Traits that are produced by two or more genes are called. Holt McDougal Biology 5 Extending Mendelian Genetics Section 2: Complex Patterns of Inheritance
Section 3: Gene Linkage and Mapping KEY CONCEPT Genes can be mapped to specific locations on chromosomes. VOCABULARY linkage map MAIN IDEA: Gene linkage was explained through fruit flies. Fill in the blank or circle the word or phrase that best completes the statement. 1. Gene linkage describes genes that are on the same chromosome and tend to be inherited separately / together. 2. Fruit flies were useful in Morgan s research, because many generations of fruit flies could be grown slowly / quickly, and fruit flies had traits that were easy / difficult to observe. 3. A wild type differs from a mutant type. A wild type is the least common / most common phenotype, and a mutant type is a much less / much more common phenotype. 4. Morgan made several conclusions from his research on fruit flies: Linked genes are on the same. Chromosomes, not genes, assort during meiosis. Homologous genes can be exchanged through during meiosis. 5. The sequence diagram on the following page shows how scientific work progressed in the discovery of gene linkage. Place the statements below into appropriate boxes in the diagram on the next page. Some statements may go into more than one box. a. Studied fruit flies. b. Studied pea plants. c. Suggested that genes assort independently of one another. d. Suggested that chromosomes assort independently. e. Suggested that some genes are linked. f. Concluded that linked genes were on the same chromosome. Holt McDougal Biology 6 Extending Mendelian Genetics Section 3: Gene Linkage and Mapping
continued Mendel: Punnett, Bateson: Morgan: MAIN IDEA: Linkage maps estimate distances between genes. Circle the word or phrase that best completes the statement. 6. The distance between two genes is related to the chance that they are inherited together. The closer / farther apart genes are, the more likely they will be inherited together. The closer / farther apart they are, the more likely they are to be separated. 7. The basis of Sturtevant s research was the hypothesis that the frequency of cross-overs during meiosis / mitosis is related to the distance between genes. 8. What is a linkage map? a. A map of each gene s phenotype relative to other genes. b. A map of each gene s shape relative to other genes. c. A map of the relative locations of genes on a chromosome. d. A map of the relative sizes of genes on a chromosome. 9. How are cross-over frequencies related to linkage maps? a. The percentage of cross-overs is added to the map linkages. b. The percentage of cross-overs is converted into map units. c. The percentage of cross-overs is generated by map units. d. The percentage of cross-overs is subtracted from the percentage of linkages. 10. What two things do linkage maps show about genes on a chromosome? a. An estimate of physical distance between genes. b. The actual physical distance between genes. c. The relative locations of genes. d. The relative sizes of genes. Holt McDougal Biology 7 Extending Mendelian Genetics Section 3: Gene Linkage and Mapping
continued 11. Use the cross-over frequencies given below to draw a linkage map for the four genes listed. Think about the relationship between cross-over frequency and distance in linkage map units. Use Figure 3.3 to help you make the linkage map. Put gene A on the far left of the map, then work through the distances between the gene pairs. Cross-over Frequencies: Linkage Map A-B 20% B-C 5% A-C 25% A-D 7% D-B 13% D-C 18% Holt McDougal Biology 8 Extending Mendelian Genetics Section 3: Gene Linkage and Mapping
Section 4: Human Genetics and Pedigrees KEY CONCEPT A combination of methods is used to study human genetics. VOCABULARY pedigree karyotype MAIN IDEA: Human genetics follows the patterns seen in other organisms. 1. Circle two ways in which genetic inheritance follows similar patterns in all sexually reproducing organisms. a. All chromosomes can be mapped on a single linkage map. b. Chromosomes assort independently during meiosis. c. Genes determine the same phenotypes. d. Relationships among alleles are the same. 2. Single-gene traits are useful in studying human genetics because: a. inheritance is always recessive. b. inheritance is independent of the gene. c. inheritance is straight-forward. d. inheritance is exponential. MAIN IDEA: Females can carry sex-linked genetic disorders. Circle the word or phrase that best completes the statement. 3. Both males and females with a recessive disorder-causing allele can be carriers of a(n) sex-linked / autosomal disorder and pass on the disorder to their offspring. 4. Males / Females are not carriers of sex-linked genetic disorders, because they cannot a normal, dominant allele to mask the effect of a recessive, disorder-causing allele. MAIN IDEA: A pedigree is a chart for tracing genes in a family. Fill in the blank with the word or phrase that best completes the sentence. 5. A pedigree is a chart that traces phenotypes and in a family. 6. In pedigree analysis, the is used to infer the genotype. Holt McDougal Biology 9 Extending Mendelian Genetics Section 4: Human Genetics and Pedigrees
continued 7. A pedigree can tell you whether a gene is most likely on an autosome or on a sex chromosome. The gene is most likely autosomal if: a. only males show the phenotype. b. all females and a few males show the phenotype. c. all males and a few females show the phenotype. d. approximately the same number of males and females show the phenotype. 8. Complete the chart to follow the logic necessary to fill out a pedigree for a sex-linked gene. Use X D and X d for the dominant and recessive X-linked genes, respectively. Tracing Sex-Linked Genes Phenotype Female, recessive phenotype Male, recessive phenotype Genotype X D X d Parental Phenotype Parental Genotype could Offspring Genotypes Female carrier, normal male could Female carrier, male with recessive phenotype could Female with recessive phenotype, normal male could Female with recessive phenotype, male with recessive phenotype could Holt McDougal Biology 10 Extending Mendelian Genetics Section 4: Human Genetics and Pedigrees
continued MAIN IDEA: Several methods help map human chromosomes. Fill in the blank with the word or phrase that best completes the sentence. 9. Two methods that are used to directly study human chromosomes are and. 10. A karyotype can show any large-scale changes in. Vocabulary Check Fill in the blank with the word that best completes the sentence. 11. A karyotype is a of all the chromosomes in a cell. Holt McDougal Biology 11 Extending Mendelian Genetics Section 4: Human Genetics and Pedigrees