1. Chapter 4, Section 2 Human Genetic Disorders
Monday, December 14, 2009

2. Objectives
Describe the causes and symptoms of five human genetic disorders.
Explain how genetic disorders are diagnosed.
Describe the role of a genetic counselor.

3. Vocabulary Words
Genetic disorder
Amniocentesis
Karyotype

4. Genetic Disorder
An abnormal condition that a person inherits through genes or chromosomes.
Caused by mutations, or changes in a person’s DNA.
In some cases, this occurs during meiosis.
In other cases, it was present in the parent’s cells that are passed on to the offspring.

5. Cystic Fibrosis
Body produces abnormally thick mucus in the lungs and intestines.
Breathing is difficult.
Bacteria grow in the mucus causing infections.
Digestion is difficult.
Mutation for CF is carried on a recessive allele.
Most common among individuals of Northern European descent.
No cure -- many on drug therapy.

6. Sickle-Cell Disease Genetic disorder affecting the blood.
Affects the production of an important protein called hemoglobin.
This protein carries oxygen.
People with Sickle-Cell produce an abnormal form of hemoglobin.
Sickle-shaped red blood cells cannot carry as much oxygen as normal-shaped cells.

7. Sickle-Cell Disease -- Cont’d
People with Sickle-Cell disease suffer from lack of oxygen in the blood.
Disease occurs most often in people of African ancestry.
They experience pain and weakness.
There is no cure.

8. Hemophilia
A genetic disorder in which a person’s blood clots very slowly or not at all.
The protein for clotting is not produced.
Caused by a recessive allele on the X chromosome.
Occurs most often in males.

9. Huntington’s Disease
A genetic disorder that is caused by a dominant allele.
The disease is fatal.
Symptoms don’t usually occur until age 30.
Causes gradual breakdown of cells in the brain.

10. Down Syndrome Result of too many or too few chromosomes.
Most have an extra copy of chromosome 21.
Error in meiosis.
Chromosomes fail to separate properly.
Degrees of retardation and limitations.
Distinctive physical appearance.
Extra chromosome 21

11. Diagnosing Genetic Disorders
Doctors use tools such as amniocentesis and karyotype to detect genetic disorders.

12. Amniocentesis A procedure used before the baby is born.
A very long needle is inserted in the abdomen to remove a small amount of the fluid that surrounds the baby.
The fluid contains cells from the baby.

13. Karyotype It is a picture of all the chromosomes in a cell.
All chromosomes are arranged in pairs.
Reveals whether the developing baby has the correct number of chromosomes.
This is a normal karyotype.

14. Homework
Workbook 4.2 (due 12/16)
No vocabulary quiz!