Genetic Disorders
By: Tanner and Jack

Definition
• A disease that is caused by an abnormality in a an individual's DNA.

Level 1: Single-Gene Disorders
• Disorders result when a mutation causes the protein product of a single gene to be altered or missing.
• Examples: Cystic fibrosis, Sickle cell disease,
Neurofibromatosis 1, etc…

Level 2- Chromosome Abnormalities
In these disorders, entire chromosomes, or large segments of them, are missing, duplicated, or otherwise altered.
Examples: Williams Syndrome, Down Syndrome,
Maple Syrup Urine Disease, Huntington’s disease, etc…

Level 3: Multifactorial Disorders
• Multifactorial disorders result from mutations in multiple genes, often coupled with environmental causes.
• Examples: Alzheimer’s disease, Breast/Ovarian cancer, Colon cancer, etc…

Recessive Disorders
• Most human genetic disorders are recessive
• Heterozygous and homozygous recessive parents can transfer to childeren
• Most people with disorders receive it from their parents who are both heterozygotes, or carriers of the recessive allele

Albinism
• Symptoms include lack of pigment in skin, hair, and eyes
• 1/22,000 people

Cystic Fibrosis
• Symptoms include excess mucus in lungs, digestive tract, liver, an increased susceptibility to infections, and death in early childhood unless treated
• 1/1,800 European-Americans

Phenylketonuria (PKU)
• Symptoms include accumulation of phenylalanine in blood, lack of normal skin pigment, mental retardation unless treated
• 1/10,000 in U.S. and Europe

Sickle-cell Disease
• Symptoms include sickled red blood cells, and damage to many tissues
• 1/500 African-Americans

Tay Sachs Disease
• Symptoms include lipid accumulation in brain cells, mental deficiency, blindness, and death in childhood
• 1/3,500 European Jews

Dominant Disorders
• Much less common than recessive disorders.
• Heterozygous and Homozygous dominant parents can transfer to children

Achondroplasia (Dwarfism)
• Head and torso develop normally while the arms and legs are short.
• Homozygous dominant genotype results in death of the embryo.
• Only heterozygotes have this disorder.
• Those with achondroplasia have a 50% chance of passing the condition to their children
• 1/25,000

Alzheimer’s Disease
• Symptoms include mental deterioration that usually happens later in life.
• Likelihood is unknown.

Huntington’s Disease
• Symptoms include mental deterioration and uncontrollable movements that usually strike in mid-aged people.
• Once deterioration begins, it is irreversible and fatal.
• Any child born to a parent with the allele has a
50% chance of inheritance.
• 1/25,000