Human Genetic Disorders

7th Grade ScienceMr. Bombick

Major Categories of Genetic Disorders

• Point Mutations• Gene(s) Deletion(s)• Chromosomal Aberrations• Polygenic

Point Mutations

• Point mutations are changes within a particular gene

• Point mutations can be the incorrect insertion or deletion of single nucleotides

• A point mutation can result in an altered gene product (protein) or no gene product (protein) being made

• A point mutation may result in no abnormality, a lethal situation, or a genetic disease

Examples of Genetic Disease Resulting from Point

Mutations

• Cystic Fibrosis• Huntington’s Disease• Color Blindness (sex-linked)• Hemophelia (sex-linked)• Sickle-Cell Disease (incomplete

dominance)• Phenylketonuria (PKU)• Tay-Sachs Disease• Crohn’s Disease

Examples of Genetic DiseaseResulting from Gene(s)

Deletion(s)

• Duchenne Muscular Dystrophy (sex-linked)

• Cri du chat• Cystic Fibrosis• DiGeorge Syndrome

Types of Chromosomal Aberrations

• Chromosomal rearrangement

• Extra chromosomes• Chromosomal deletions

Examples of Genetic DiseaseResulting from Chromosomal

Aberrations

• Down syndrome (Trisomy of 21)• Kleinfelter’s syndrome (XXY)• Turner syndrome (single X)• Triple XXX syndrome• Philadelphia chromosome

translocation-chronic myelogenous leukemia (CML)

Examples of Genetic Diseasefrom Complex and polygenic

Factors

Genetic disorders may be complex and polygenic meaning that they are likely associated with the effects of multiple genes in combination with lifestyle and environmental factors. Although complex disorders often cluster in families, they do not have a clear-cut pattern of inheritance. This makes it difficult to determine a person’s risk of inheriting or passing on these disorders. Complex disorders are also difficult to study and treat because the specific factors that cause most of these disorders have not yet been identified.

Examples of Polygenic Genetic Disorders

• Asthma• Auto-immune diseases (e.g., MS)• Cancers• Cleft palate• Diabetes• Heart disease• Hypertension• Inflammatory bowel disease• Mental retardation• Mood disorders• Obesity• Infertility

The End