Chromosomally transmitted form of mental retardation
Causes lifelong mental retardation, developmental delays and other problems.
Varies in severity, developmental problems range from moderate to serious.
Typically (90% of cases) caused by Trisomy 21 (trisomy 21 has three copies of chromosome 21 — instead of the usual two copies — in all of his or her cells).
Caused by abnormal cell division during the development of the sperm cell or the egg cell
Disorder in males; extra X chromosome
Physical development: XXY males have weak muscles and reduced strength
Social development: As babies, XXY males tend to be quiet and undemanding
Language development: As boys, between 25 percent and 85 percent of XXY males have some kind of language problem
Disorder in males; extra Y chromosome
Affected individuals are usually very tall and thin. Many experience severe acne during adolescence. Additional symptoms may include antisocial or behavioral problems and learning disabilities. Intelligence is usually normal, although IQ, on average, is 10 to 15 points lower than siblings.
Fragile X Syndrome
Abnormality in X chromosome;becomes constricted or breaks
Physical features: enlarged ears, long face with prominent chin, and large testicles (in post pubertal males) are common.
Connective tissue problems: may include ear infections, mitral valve prolapse, flat feet, double-jointed fingers, hyperflexible joints and a variety of skeletal problems.
Behavioral characteristics: in males include attention deficit disorders, speech disturbances, hand biting, hand flapping, autistic behaviors, poor eye contact, and unusual responses to various touch, auditory or visual stimuli.
Female disorder; X chromosome missing or partially deleted
can cause a variety of medical and developmental problems, including short stature, failure to begin puberty, infertility, heart defects and certain learning disabilities.
The field that seeks to discover the influence of heredity and environment on individual differences in human traits and development.
ENVIRONMENT EFFECT: Child is the passive recipient of environments which fit genotype.
ENVIRONMENT EFFECT: Child evokes environment as a result of genetic influences (temperament).
ENVIRONMENT EFFECT (NICHE-PICKING): Child seeks out environments as a result of genetic influences (e.g., thrill seeker)
Any agent that causes a birth defect
Severity and type of defect affected by
Dose, genetic susceptibility, time of exposure
Length: 6 weeks Key Events: Arms, legs, face organs and muscles all develop. Heart begins beating