Human Genetics Handout Spr08

Human Genetics Handout Spr08 - BSC 2011 HUMAN INHERITANCE...

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BSC 2011 HUMAN INHERITANCE PLEASE NOTE: you are responsible for knowing the name, genetic basis, and general description of the conditions marked by three asterisks (***) Another note: More information about the genetic traits and diseases described here, as well as for thousands of other human genetic traits, can be found at the website Online Mendelian Inheritance in Man at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM&cmd=Limits: . Each disease or trait is assigned a catalogue number (MIM/OMIM number), and these catalogue numbers are given in parentheses below to help you explore these topics further. AUTOSOMAL RECESSIVE ***Albinism (203100): The gene for production of the pigment melanin is non-functional in the homozygous recessive state. Characterized by the absence of color in the skin and hair, the eyes of an affected individual appear red due to the exposure of the underlying blood vessels. Frequency = 1/10,000 live births. ***Cystic Fibrosis (219700): One of the most common serious genetic diseases among Caucasians. It results from a mutation in the gene responsible for the proteins that transport chlorine ions across cell membranes. With CF, the high extracellular chloride ion concentrations result in abnormally thick mucous (glycoproteins) that coats the lungs, intestines, and pancreatic ducts, blocking the normal functions of those organs. In 1950, the average life expectancy for a child with CF was four years; improved medical intervention has raised the mean survival time to over 30 years. The gene has recently been cloned, so there is reason to hope for rapid progress towards even better treatment. Primarily found in Caucasians, the frequency in the U.S. white population = 1/2,000 live births. Erythroblastosis Fetalis: An old problem that occurred when an Rh+ fetus was carried by an Rh- mother. The singular condition of risk is an Rh+ father, an Rh- mother, and an Rh+ fetus. Exchange of blood during or at the end of pregnancy can result in antibodies being formed by the mother to the Rh+ red blood cells of the fetus. This can cause death of a subsequent Rh+ fetus, if not treated. This problem is now treatable by a manufactured gamma globulin (RHOGAM) which removes the Rh antibodies from the mother's blood stream. Incidentally, while long believed to be a standard two allele system with complete dominance (Rh+ > Rh-), it is now apparent that the Rh blood group is more complex, but it is not clear if it consists of a single gene with multiple alleles or a group of very closely linked genes that together determine Rh blood type. ***Galactosemia (230400): An enzyme deficiency disease preventing the utilization of lactose (milk sugar). The sugar galactose accumulates in the brain causing severe mental retardation and early death if not treated. The condition is readily detectable at birth and is treated via a lactose-free diet. Frequency = 1/200,000 live births.
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