Genetic Disorders Autosomal and Sex-linked

HOW DO WE GET GENETIC DISORDERS? Nondisjunction – failure of chromosomes to separate during cell division. Results in too many or too few chromosomes.

KARYOTYPE - Chart that shows the size, number, and shape of all chromosomes in an organism.

Patau syndrome, trisomy 13  1:5000 live births.  Lifespan – about a few months  Complications include: congenital heart disease, lack of breathing, deafness, feeding problems, heart failure, seizures, vision problems.

Edwards syndrome, trisomy 18  Lifespan – Most pass in first month, about 10% live past first year.  NOT inherited.  Complications include: low birth weight, small head, heart defects, organ abnormalities, fists with overlapping fingers.

Down’s syndrome, trisomy 21  Affects 1:700 children  Lifespan – Usually to adults, but shorter lifespan overall.  Complications include: characteristic facial features, short stature, heart defects respiratory disease, Alzheimer’s and leukemia, often sterile, mental retardation.  More prevalent with older mothers. Can be due to nondisjunction of father’s chromosome 21.

Cri-du-chat, deletion in 5  Abnormal rate of growth of the larynx (cry of the cat).  More common in females by 3:1 ratio.  Lifespan – generally normal  Complications include: microcephaly (small head), slow development, poor muscle tone, congenital heart defect, mental retardation.

Jacobs, XYY  All male.  Affected – 1:1000 males have XYY.  Complications include: some taller, risk of learning disabilities, delayed language skills, behavioral problems.  Most males able to conceive children!

Turner’s, X0  Lifespan – slightly reduced  1:2500 females.  Complications include: short, broad chest, low hairline, reproductively sterile, obesity, small fingernails

Klinefelter’s, XXY  Affects 1:750 males  Lifespan – normal.  Underdiagnosed.  Complications include: low testosterone, less body hair/less muscular as teenager, often taller. More likely to get breast cancer, autoimmune disorders, and osteoporosis.

Triple X, XXX  The one to get!  Affects 1:1000 females  Lifespan – Normal  No complications! Fertile and healthy.  Cannot tell difference between Triple X and normal female.

Philadelphia translocation, 9 to 22 translocation  Affects - 1-2:10,000 newborns  Specific chromosomal abnormality that is associated with chronic myelogenous leukemia (CML).  95% of people with CML have this abnormality.

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