1. 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

2. 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.

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

4. 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.

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

6. 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.

7. 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.

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

9. Effects of Gene Location, continued
Section 1 Chromosomes and Inheritance
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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.

10. 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.

11. 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.

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

13. 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.

14. 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.

15. 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.

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

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

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

19. 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.

20. Genetic Traits and Disorders, continued
Section 2 Human Genetics
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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.

21. Multiple Alleles

22. Comparing Single Allele, Multiple Allele, and Polygenic Traits
Section 2 Human Genetics
Chapter 12
Comparing Single Allele, Multiple Allele, and Polygenic Traits

23. Comparing Complete, Incomplete, and Co-Dominance
Section 2 Human Genetics
Chapter 12
Comparing Complete, Incomplete, and Co-Dominance

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

25. Genetic Traits and Disorders, continued
Section 2 Human Genetics
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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. Chapter 12 Comparing X-Linked and Sex-Influenced Traits
Section 2 Human Genetics
Chapter 12
Comparing X-Linked and Sex-Influenced Traits

27. 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.

28. 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.

29. Section 2 Human Genetics
Chapter 12
Genetic Disorder

30. 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.