1. Genetic Disorders Cystic Fibrosis
Caused by a recessive allele on chromosome 7
It is inherited in a autosomal recessive pattern.
People with cystic fibrosis lack one amino acid in the CFTR gene, causing a thick mucus that clogs the lungs.

2. Genetic Disorders Ideogram: A diagram of a chromosome
Ideograms show can show the position of specific genes:
The CFTR gene is located at 7q31.2
7th chromosome
q = long arm of the chromosome
(p = short arm of the chromosome)
31.2 represents the position on the arm (band number)

3. Genetic Disorders Huntington’s Disease Caused by a dominant allele
The DNA sequence – C A G – is repeated over several times.
This causes the Huntingin protein to become deformed which damages the nervous system.
Most genetic disorders are inherited as a recessive trait.
Why are dominant genetic disorders more rare than recessive disorder?

4. Genetic Disorders
Why does Huntington’s disorder get passed from generation to generation.
Causes gradual damage to the nervous system resulting in loss of muscle control and mental function.
People who have the disease show no symptoms until their thirties or forties (after they passed the allele to their children).

5. Genetic Disorders Sickle Cell Disease
Characterize by “sickle” shaped red blood cells
Caused by a mutation of the hemoglobin gene on chromosome 11.
People who are heterozygous for the sickle cell trait have both normal and sickle shaped red blood cells.
What is the pattern of inheritance

6. Genetic Disorders
Sickle Cell allele is carried by 1 in 12 of African ancestry
Most genetic disorders are extremely rare. Why is sickle cell so common?
Those who are heterozygous for Sickle cell are resistant to malaria.
The benefits of being heterozygous outweighed the risks the of passing on both parents passing the allele for the disease.

7. Disorders Caused by Individual Genes
PKU, or phenylketonuria
Caused by a recessive allele found on chromosome 12
Phenylalanine is an amino acid found in milk and other foods
People who lack the enzyme needed to break down phenylalanine have the amino acid build up in tissues and cause severe mental retardation.