Section 2 Human GeneticsChapter 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.

Section 2 Human GeneticsChapter 12

Inheritance of Traits

• Pedigrees – Geneticists use pedigrees to trace diseases or

traits through families. – Pedigrees are diagrams that reveal inheritance

patterns of genes.

Chapter 12Section 2 Human Genetics

Pedigree for Cystic Fibrosis

Chapter 12

Some Important Genetic Disorders

Section 2 Human Genetics

Autosomal recessive disorders

a. Tay Sachs

b. PKU- Phenylketonuria

c. Albinism

d. cystic fibrosis

Sickle-Cell Anemia (Autosomal Recessive)

Huntington’s Disease (Autosomal Dominant)

Autosomal Dominant

a. achondroplasia (dwarfism)

b. 15 year girls

Section 2 Human GeneticsChapter 12

Genetic Traits and Disorders

• Polygenic Inheritance– Polygenic characters, such as skin color, are

controlled by two or more genes.

Section 2 Human GeneticsChapter 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.

Section 2 Human GeneticsChapter 12

Detecting Genetic Disease

• Genetic counseling informs screened individuals about problems that might affect their offspring.

Section 2 Human GeneticsChapter 12

Detecting Genetic Disease

• Genetic screening examines a person’s genetic makeup through blood test.

Section 2 Human GeneticsChapter 12

Detecting Genetic Disease

• Amniocentesis and chorionic villi sampling help physicians test a fetus for the presence of genetic disorders.

• Ultrasounds

Chapter 12

Click below to watch the Visual Concept.

Visual Concept

Comparing Single Allele, Multiple Allele, and Polygenic Traits

Section 2 Human Genetics

Chapter 12

Click below to watch the Visual Concept.

Visual Concept

Comparing Complete, Incomplete,and Co-Dominance

Section 2 Human Genetics

Chapter 12

Click below to watch the Visual Concept.

Visual Concept

Comparing X-Linked and Sex-Influenced Traits

Section 2 Human Genetics

Section 2 Human GeneticsChapter 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.