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

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.

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

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.

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

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.

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.

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.

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.

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.

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.

Chromosomal Mutations Section 1 Chromosomes and Inheritance Chapter 12 Chromosomal Mutations

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.

Section 1 Chromosomes and Inheritance Chapter 12 Gene Mutations

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.

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.

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.