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