Topic Index

Medical Genetics Home

Overview of Birth Defects

Chromosome Abnormalities

Overview of Chromosome Abnormalities

Types of Chromosome Abnormalities

Numerical Abnormalities: Overview of Trisomies and Monosomies

Down Syndrome (Trisomy 21)

Trisomy 18 & 13

Turner Syndrome

Structural Abnormalities: Deletions (Cri du Chat) and Duplications (Pallister Killian)

Translocations

Translocation Down Syndrome

Other Arrangements: Rings and Inversions

Mosaicism

Mosaic Down Syndrome

How Chromosome Abnormalities Happen: Meiosis, Mitosis, Maternal Age, Environment

Chance a Chromosome Abnormality Will Occur Again: Numerical, Structural (Inherited and De Novo), Mosaicism

Single Gene Defects

Overview of Single Gene Defects

Autosomal Dominant: Marfan Syndrome

Autosomal Recessive: Cystic Fibrosis, Sickle Cell Anemia, Tay Sachs Disease

X-linked Recessive: Red-Green Color Blindness, Hemophilia A

X-linked Dominant: Incontinentia Pigmenti

The Difference Between a Chromosome Abnormality and a Single Gene Defect

Multifactorial Inheritance

Teratogens

Examples of Teratogens

Fetal Alcohol Syndrome (FAS)

Phenytoin (Dilantin)

Varicella

Examples of Non-Teratogenic Agents: Spermicides, Acetaminophen, Prenatal Vitamins, Using a Microwave to Cook Food

Identifying Teratogens

Non-Traditional Inheritance

Uniparental Disomy: Prader-Willi Syndrome, Angelman Syndrome

Trinucleotide Repeats: Fragile-X Syndrome

Mitochondrial Inheritance: Leber's Optic Atrophy

Evaluating a Child for Birth Defects

Overview of Newborn Screening for Birth Defects

Medical History and Genetic Testing

Testing for Birth Defects

Chromosome Studies: Karyotype, Extended Banding, Fluorescent In Situ Hybridization (FISH)

Studies for Single Gene Defects: DNA (Direct and Indirect)

Biochemical Genetic Testing

Uses of Genetic Testing

Genetic Services: When, Where, How

Identification, Treatment, and Prevention of Birth Defects

The Human Genome Project

Vitamin, Gene, and Enzyme Replacement Therapy

Before Your Next Pregnancy

When to Seek Genetic Counseling

Glossary

Support Groups

Online Resources