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
Teratogens Overview
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, Fluorescence In Situ Hybridization (FISH), and Chromosomal Microarray Analysis
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