1. Human Genetic Disorders
Learning Targets:
What are two major causes of genetic disorders in humans?
How do geneticists trace the inheritance of traits?
How are genetic disorders diagnosed and treated?

2. Key Terms
Genetic disorder
Karyotype
pedigree

3. Causes of Genetic Disorders
Genetic disorder – abnormal condition that a person inherits through genes or chromosomes
Some are caused by mutations in the DNA of genes
Others are caused by changes in the overall structure or number of chromosomes

4. Cystic Fibrosis
Body produces abnormally thick mucus in the lungs and intestines
The thick mucus fills the lungs making it hard to breathe
Caused by recessive
allele on one chromosome
that is the result of a
mutation in which 3 base
pairs are removed from a
DNA molecule

5. Sickle- Cell Disease
Affects hemoglobin, protein in blood that carries O2
When O2 concentrations are low blood cells have a sickle shape
The sickle shape can clog blood vessels and cannot carry as much O2 as normal shaped red blood cells
The allele is codominant with normal allele
A person with 2 sickle shaped alleles will have the disease
One allele and the person will produce both normal and sickle shaped cells. These people will not usually have symptoms of the disease

6. Hemophilia A person’s blood clots very slowly or not at all
Do not produce one of the proteins needed for normal blood clotting
Small bumps and bruises may cause internal bleeding that can’t be controlled
Caused by a recessive allele on the X chromosome
Sex-linked disorder – occurs more frequently in males

7. Down Syndrome Trisomy 21
Have an extra copy of chromosome 21 (instead of
a pair the person has 3 copies)
Most often occurs when chromosomes fail to separate properly during meiosis
Have some degree of mental retardation.
Heart defects are also common, but can be treated

8. Pedigrees Chart used to trace the inheritance of traits in humans
Can track ordinary traits or a genetic disorder

9. Managing Genetic Disorders
Doctors used to only have Punnett Squares and pedigrees to help predict genetic disorders
Now they have tools such as karyotypes to help diagnose genetic disorders
People with genetic disorders can be helped through medical care, education, job training, and other methods

10. Karyotypes Picture of all the chromosomes in a cell Arranged in pairs
Can reveal whether a person has the correct number of chromosomes

11. Genetic Counseling
A couple with a family history of a genetic disorder can go to a genetic counselor for advice
Help couples understand their chances of having a child with a
particular genetic disorder

12. Dealing with Genetic Disorders
Medical treatments help people with some disorders
Ex. Physical therapy helps remove mucus from the lungs of people with cystic fibrosis
Taking Folic Acid helps people with sickle-cell disease make more red blood cells
Education and job training helps people with Down Syndrome find work in a variety of places of employment