• The physical characteristics of an individual are controlled by inherited genes.
  
  
• Dominant genetic traits appear if a single dominant allele is inherited; recessive genetic traits require the inheritance of two recessive alleles.

1. What determines the physical characteristics of an individual?
   Answer
   
   
2. When do dominant traits appear? When do recessive traits appear?
   Answer

Essential Study Partner

• Introduction

• It is possible to determine the chances of an offspring inheriting a particular parental gene, and therefore a particular condition.
  
  
• Pedigree charts are used to determine the pattern of inheritance for a condition that runs in the family.

1. How is it possible to recognize an autosomal dominant or recessive trait from the pattern of inheritance?
   Answer
   
   
2. What are some examples of inherited genetic disorders?
   Answer
   
   
3. What types of alleles must be inherited to exhibit a recessive genetic disorder? What type of alleles can be inherited to exhibit a dominant genetic disorder?
   Answer

Essential Study Partner

• Monohybrid Cross

• Certain traits, such as skin color, behavior, and various syndromes, are polygenic.
  
  
• Blood type is controlled by multiple alleles.
  
  
• Some traits, like sickle-cell disease, are incompletely dominant.

1. What are some examples of human polygenic traits?
   Answer
   
   
2. How is blood type an example of codominance?
   Answer
   
   
3. What are some examples of incomplete dominance in humans?
   Answer

Art Quiz

• Correlation Between Sickle Cell Allele and Malaria

• Sex-linked traits are usually carried on the X chromosome. Males, with only one X, are more likely to express X-linked traits.
  
  
• Some traits are sex-influenced rather than sex-linked.

1. Do the sex chromosomes determine other traits besides an individual's gender?
   Answer
   
   
2. Why do males exhibit X-linked disorders more often than females?
   Answer

Essential Study Partner

• Sex Chromosomes

Art Quiz

• Patterns of Inheritance

Bioethical Focus

• Genetic Profiling

Chapter Summary

Exploration

• Heredity in Families