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2. Standardized Test Prep
Resources
Chapter Presentation
Visual Concepts
Transparencies
Standardized Test Prep

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

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

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

6. Chromosomes, continued
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. Karyotypes: Male and Female
Section 1 Chromosomes and Inheritance
Chapter 12
Karyotypes: Male and Female

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

11. Effects of Gene Location, continued
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. Chapter 12 Mutations Germ-cell mutations occur in gametes and can be
Section 1 Chromosomes and Inheritance
Chapter 12
Mutations
Germ-cell mutations occur in gametes and can be
passed on to offspring.
Somatic-cell mutations occur in body
cells and affect only the individual organism.

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

14. Chromosomal Mutations
Section 1 Chromosomes and Inheritance
Chapter 12
Chromosomal Mutations

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

16. Section 1 Chromosomes and Inheritance
Chapter 12
Gene Mutations

17. Section 1 Chromosomes and Inheritance
Chapter 12
Gene Mutations

18. Section 2 Human Genetics
Chapter 12
Objectives
Analyze pedigrees to determine how genetic traits and genetic disorders are inherited.
Summarize the different patterns of inheritance seen in genetic traits and genetic disorders.
Explain the inheritance of ABO blood groups.
Compare sex-linked traits with sex-influenced traits.
Explain how geneticists can detect and treat genetic disorders.

19. Chapter 12 Inheritance of Traits Pedigrees
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.

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

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

22. Genetic Traits and Disorders
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.

23. Genetic Traits and Disorders, continued
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.

24. Genetic Traits and Disorders, continued
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.

25. Comparing Single Allele, Multiple Allele, and Polygenic Traits
Section 2 Human Genetics
Chapter 12
Comparing Single Allele, Multiple Allele, and Polygenic Traits
Click below to watch the Visual Concept.
Visual Concept

26. Comparing Complete, Incomplete, and Co-Dominance
Section 2 Human Genetics
Chapter 12
Comparing Complete, Incomplete, and Co-Dominance
Click below to watch the Visual Concept.
Visual Concept

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

28. Genetic Traits and Disorders, continued
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.

29. Chapter 12 Comparing X-Linked and Sex-Influenced Traits
Section 2 Human Genetics
Chapter 12
Comparing X-Linked and Sex-Influenced Traits
Click below to watch the Visual Concept.
Visual Concept

30. Detecting Genetic Disease
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.

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

32. Treating Genetic Disease
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.

33. Chapter 12 Genetic Disorder Section 2 Human Genetics
Click below to watch the Visual Concept.
Visual Concept

34. Treating Genetic Disease, continued
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.

35. Chapter 12 Multiple Choice 1. Which can a chromosomal map show?
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

36. Multiple Choice, continued
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

37. Multiple Choice, continued
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

38. Multiple Choice, continued
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

39. Multiple Choice, continued
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

40. Multiple Choice, continued
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

41. Multiple Choice, continued
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.

42. Multiple Choice, continued
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.

43. Multiple Choice, continued
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.

44. Multiple Choice, continued
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.

45. Multiple Choice, continued
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

46. Multiple Choice, continued
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

47. Multiple Choice, continued
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

48. Multiple Choice, continued
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

49. Chapter 12 Short Response
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?

50. Short Response, continued
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.

51. Chapter 12 Extended Response
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.

52. Extended Response, continued
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.