1. Human Genetic Disorders

2. Genetic Disorder
An abnormal condition that a person inherits through genes or chromosomes.
Caused by mutations, or changes in a person’s DNA
May occur during meiosis or may also have been already present in the parent’s cells

3. Cystic Fibrosis Chromosome # 7 CFTR gene
The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein.
Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane.
The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.

4. Cystic Fibrosis Prognosis
Not sex-linked
No cure
Drugs to prevent infection
Physical therapy to break up mucus in lungs

5. Sickle-Cell Anemia
Genetic disorder that causes the production of abnormal hemoglobin.
Hemoglobin is a protein in RBCs that carriers oxygen.
Sickle-shape often blocks blood vessels resulting in lack of oxygen.

6. Genetics Behind Sickle-Cell
9% of African Americans carry the sickle-cell allele
Sickle-cell allele is codominant with normal allele
Leads to resistance to malaria
2 Sickle-cell alleles results in sickle-cell symptoms

7. Hemophilia
Genetic disorder in which a person’s blood clots very slowly or not at all.
Individuals can bleed to death from a minor cut or scrape.
Caused by recessive allele on the X chromosome.
Treatment
Receive doses of missing clotting protein
Can lead relatively normal lives

8. Down Syndrome Every cell has an extra copy of chromosome 21.
Result of error during meiosis
Distinctive physical appearance and some degree of mental retardation
Many lead full, active lives.

9. Tools in Diagnosing Genetic Disorders
Amniocentesis
Very long needle used to remove small amount of fluid that surrounds the baby
Fluid contains cells from the baby
Karyotype
Picture of all the chromosomes in a cell
Can reveal whether a developing baby has the correct number of chromosomes in its cells and whether it is a boy or girl.

10. Genetic Counseling
Helps couples understand their changes of having a child with a particular genetic disorder.
Uses karyotypes, pedigree charts, and Punnett squares to determine if parents are carriers, etc.

11. Summary Questions
Explain how genetic disorders occur in humans. Give two examples of genetic disorders.
Describe two tools that doctors use to detect genetic disorders.
How do the cells of people with Down syndrome differ from those of others? How might this difference arise?

12. Summary Questions
A couple with a family history of hemophilia is about to have a baby girl.
What information about the parents would you want to know?
How would this information help you determine whether the baby will have hemophilia?