Human genetic disorders

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
1. Genetic disorder
2. Amniocentesis
3. 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!