• Genetic counseling can help individuals determine the risk of a chromosomal or genetic mutation in their families.
• The human karyotype contains 22 pairs of autosomes and one pair of sex chromosomes for a total of 46 chromosomes.
• It is possible to acquire chromosomes for study from fetuses to adults.
• Inheritance of an abnormal chromosome number is most likely due to nondisjunction.
• Several syndromes are the result of inheriting an incorrect number of sex chromosomes.
• Chromosome mutations are associated with various syndromes.

1. What do you call a visual display of an individual's chromosomes arranged by pairs?
   Answer
2. How is it possible to acquire chromosomes from an adult for study? To acquire fetal chromosomes?
   Answer
3. What process usually causes an individual to have an abnormal number of chromosomes?
   Answer
4. What is the specific chromosome abnormality of a person with Down syndrome?
   Answer
5. What are some syndromes that from inheritance of an abnormal sex chromosome number?
   Answer
6. What are other types of chromosomes mutations, aside from abnormal chromosome number?
   Answer

Essential Study Partner

• Introduction
• Chromosomes
• Karyotype
• Sex Chromosomes
• Abnormal Chromosomes

Art Quiz

• Nondisjunction and Sex Chromosomes

Exploration

• Exploring Meiosis: Down Syndrome

General Biology Case Studies

• Gene Banks Versus Privacy Invasion

• Pedigree charts are used to determine the pattern of inheritance for a condition that runs in the family
• Single gene mutations cause a variety of disorders.
• Protein tests, genetic markers and DNA markers are three ways of testing for genetic disorders.
• Some genetic disorders can be identified prenataly by testing the egg, the embryo, or the fetus.

1. What is a pedigree, and how do you use it to recognize an autosomal recessive/dominant disorder and X-linked recessive disorder?
   Answer
2. What are the symptoms of the genetic disorders discussed in this chapter?
   Answer
3. Presently, how is it possible to test for genetic disorders? How is it possible to test the fetus, the embryo, or the egg?
   Answer

Exploration

• Cystic Fibrosis

Explorations

• Constructing a Genetic Map
• Heredity in Families
• Gene Segregation within Families

• Genetic profiles will help to prevent and treat many conditions.
• Gene therapy is now being used to replace defective genes with healthy genes and to help cure various human ills.

1. How will a genetic profile be acquired, and how will genetic profiles be used?
   Answer
2. What is gene therapy, and how is it carried out?
   Answer

Essential Study Partner

• Gene Therapy