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2. Resources Chapter Presentation Visual Concepts Transparencies Standardized Test Prep

3. Inheritance Patterns and Human Genetics Chapter 12 Table of Contents Section 1 Chromosomes and Inheritance Section 2 Human Genetics

4. Section 1 Chromosomes and Inheritance Chapter 12 Objectives • Distinguishbetween sex chromosomes and autosomes. • Explainthe role of sex chromosomes in sex determination. • Describehow an X- or Y-linked gene affects the inheritance of traits. • Explainthe effect of crossing-over on the inheritance of genes in linkage groups. • Distinguishbetween chromosome mutations and gene mutations.

5. Section 1 Chromosomes and Inheritance Chapter 12 Chromosomes • Genes reside on chromosomes.

6. Section 1 Chromosomes and Inheritance Chapter 12 Chromosomes, continued • Sex Chromosomes and Autosomes • Sex chromosomes contain genes that determine an organism’s sex (gender). • The remaining chromosomes that are not directly involved in determining the sex of an individual are called autosomes.

7. Section 1 Chromosomes and Inheritance Chapter 12 Karyotypes: Male and Female

8. Section 1 Chromosomes and Inheritance Chapter 12 Chromosomes, continued • Sex Determination • In mammals, an individual carrying two X chromosomes is female. • An individual carrying an X and a Y chromosome is male.

9. Section 1 Chromosomes and Inheritance Chapter 12 Effects of Gene Location • Sex-Linked Genes and Traits • Genes found on the X chromosome are X-linked genes. • A sex-linked trait is a trait whose allele is located on a sex chromosome. • Because males have only one X chromosome, a male who carries a recessive allele on the X chromosome will exhibit the sex-linked trait.

10. Section 1 Chromosomes and Inheritance Chapter 12 Effects of Gene Location, continued • Linked Genes • Pairs of genes that tend to be inherited together are calledlinked genes.

11. Section 1 Chromosomes and Inheritance Chapter 12 Effects of Gene Location, continued • Chromosome Mapping • The farther apart two genes are located on a chromosome, the more likely a cross-over will occur. • Researchers use recombinant percentages to construct chromosome maps showing relative gene positions.

12. Section 1 Chromosomes and Inheritance Chapter 12 Mutations • Germ-cell mutationsoccur in gametes and can be passed on to offspring. • Somatic-cell mutationsoccur in body cells and affect only the individual organism.

13. Section 1 Chromosomes and Inheritance Chapter 12 Mutations, continued • Chromosome Mutations • Chromosome mutationsare changes in the structure of a chromosome or the loss or gain of an entire chromosome.

14. Section 1 Chromosomes and Inheritance Chapter 12 Chromosomal Mutations

15. Section 1 Chromosomes and Inheritance Chapter 12 Mutations, continued • Gene Mutations • Gene mutationsare changes in one or more of the nucleotides in a gene.

16. Section 1 Chromosomes and Inheritance Chapter 12 Gene Mutations

17. Section 2 Human Genetics Chapter 12 Objectives • Analyzepedigrees to determine how genetic traits and genetic disorders are inherited. • Summarizethe different patterns of inheritance seen in genetic traits and genetic disorders. • Explainthe inheritance of ABO blood groups. • Comparesex-linked traits with sex-influenced traits. • Explainhow geneticists can detect and treat genetic disorders.

18. Section 2 Human Genetics Chapter 12 Inheritance of Traits • Pedigrees • Geneticists use pedigrees to trace diseases or traits through families. • Pedigrees are diagrams that reveal inheritance patterns of genes.

19. Section 2 Human Genetics Chapter 12 Pedigree for Cystic Fibrosis

20. Section 2 Human Genetics Chapter 12 Some Important Genetic Disorders

21. Section 2 Human Genetics Chapter 12 Genetic Traits and Disorders • Polygenic Inheritance • Polygenic characters, such as skin color, are controlled by two or more genes.

22. Section 2 Human Genetics Chapter 12 Genetic Traits and Disorders, continued • Complex Characters • Complex characters, such as polygenic traits, are influenced by both genes and environment.

23. Section 2 Human Genetics Chapter 12 Genetic Traits and Disorders, continued • Multiple Alleles • Multiple-allele characters, such as ABO blood groups, are controlled by three or more alleles of a gene.

24. Section 2 Human Genetics Chapter 12 Genetic Traits and Disorders, continued • X-Linked Traits • The gene forcolorblindness, an X-linked recessive gene, is found on the X chromosome.

25. Section 2 Human Genetics Chapter 12 Genetic Traits and Disorders, continued • Sex-influenced Trait • A sex-influenced trait, such as pattern baldness, is expressed differently in men than in women even if it is on an autosome and both sexes have the same genotype.

26. Section 2 Human Genetics Chapter 12 Detecting Genetic Disease • Genetic screening examines a person’s genetic makeup and potential risks of passing disorders to offspring. • Amniocentesis and chorionic villi sampling help physicians test a fetus for the presence of genetic disorders.

27. Section 2 Human Genetics Chapter 12 Detecting Genetic Disease, continued • Genetic Counseling • Genetic counseling informs screened individuals about problems that might affect their offspring.

28. Section 2 Human Genetics Chapter 12 Treating Genetic Disease • Genetic disorders are treated in various ways. • Among the treatments are symptom-relieving treatments and symptom-prevention measures, such as insulin injections for diabetes.

29. Section 2 Human Genetics Chapter 12 Treating Genetic Disease, continued • Gene Therapy • In gene therapy, a defective gene is replaced with a copy of a healthy gene. • Somatic cell gene therapy alters only body cells. • Germ cell gene therapy attempts to alter eggs or sperm.

30. Chapter 12 Standardized Test Prep Multiple Choice 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

31. Chapter 12 Standardized Test Prep Multiple Choice, continued 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

32. Chapter 12 Standardized Test Prep Multiple Choice, continued 2. Which can result from the deletion of a single nucleotide? F. trisomy G. a translocation H. nondisjunction J. a frameshift mutation

33. Chapter 12 Standardized Test Prep Multiple Choice, continued 2. Which can result from the deletion of a single nucleotide? F. trisomy G. a translocation H. nondisjunction J. a frameshift mutation

34. Chapter 12 Standardized Test Prep Multiple Choice, continued 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

35. Chapter 12 Standardized Test Prep Multiple Choice, continued 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

36. Chapter 12 Standardized Test Prep Multiple Choice, continued 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.

37. Chapter 12 Standardized Test Prep Multiple Choice, continued 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.

38. Chapter 12 Standardized Test Prep Multiple Choice, continued The table below shows the genotypes and phenotypes of pattern baldness. Use the table to answer the question that follows. 5.Which statement best explains why men and women express the Bb genotype differently? A. The trait is polygenic. B. The trait has multiple alleles. C. Pattern baldness is a sex-linked trait. D. Pattern baldness is a sex-influenced trait.

39. Chapter 12 Standardized Test Prep Multiple Choice, continued The table below shows the genotypes and phenotypes of pattern baldness. Use the table to answer the question that follows. 5.Which statement best explains why men and women express the Bb genotype differently? A. The trait is polygenic. B. The trait has multiple alleles. C. Pattern baldness is a sex-linked trait. D. Pattern baldness is a sex-influenced trait.

40. Chapter 12 Standardized Test Prep Multiple Choice, continued 6. translocation : chromosome mutation :: substitution F. gene mutation G. point mutation H. germ-cell mutation J. somatic-cell mutation

41. Chapter 12 Standardized Test Prep Multiple Choice, continued 6. translocation : chromosome mutation :: substitution F. gene mutation G. point mutation H. germ-cell mutation J. somatic-cell mutation

42. Chapter 12 Standardized Test Prep Multiple Choice, continued The image below is a pedigree showing the inheritance of hemophilia in a family. Use the pedigree to answer the question that follows. 7. Which type of inheritance pattern is associated with hemophilia? A. autosomal recessive B. sex-linked dominant C. sex-linked recessive D. autosomal dominant

43. Chapter 12 Standardized Test Prep Multiple Choice, continued The image below is a pedigree showing the inheritance of hemophilia in a family. Use the pedigree to answer the question that follows. 7. Which type of inheritance pattern is associated with hemophilia? A. autosomal recessive B. sex-linked dominant C. sex-linked recessive D. autosomal dominant

44. Chapter 12 Standardized Test Prep Short Response Consider a couple about to get married. The woman has cystic fibrosis, but the man does not. What benefit would they gain by seeing a genetic counselor?

45. Chapter 12 Standardized Test Prep Short Response, continued Consider a couple about to get married. The woman has cystic fibrosis, but the man does not. What benefit would they gain by seeing a genetic counselor? Answer: Genetic counseling will tell them the likelihood of each of their children having cystic fibrosis or carrying the cystic fibrosis gene.

46. Chapter 12 Standardized Test Prep Extended Response Colorblindness is a recessive, sex-linked trait. A woman and a man, both with normal vision, have three daughters with normal vision. One of the daughters marries a man with normal vision, and they have a son who is colorblind. Part A Which parent of the son is the carrier of the trait? Explain your answer. Part B What is the likelihood that the children of a woman heterozygous for colorblindness and colorblind man will express the trait? Explain your answer.

47. Chapter 12 Standardized Test Prep Extended Response, continued Answer: Part A The son’s mother carries the trait. The gene for colorblindness is carried on the X chromosome. Part B Given: X-linked recessive: heterozygous female = XB (normal)Xb (colorblind); colorblind male = Xb (colorblind)Y. This Punnett square predicts that 50 percent of the children will be male and 50 percent of the children will be female. 50 percent will be colorblind and 50 percent will have normal vision. 25 percent will be males with normal vision and will not be carriers. 25 percent will be female carriers with normal vision. 25 percent will be colorblind females. 25 percent will be colorblind males.