Human Genetics

Multiple Alleles There are more than two possible genes that can be inherited for a trait. Examples Flower color Blood type

Sex-linked Traits Trait for which the gene is located on one of the sex chromosomes. XHXH ~ female, normal XHXh ~ female, normal carrier XhXh ~ female, hemophiliac XHY ~ male, normal XhY ~ male, hemophiliac

Pedigrees A family tree that shows how a particular trait is passed from parents to offspring. Be able to read and interpret

Pedigree of a Sex-linked Trait Colorblindness is sex-linked. Blue box is colorblind White box is normal vision with two normal genes. Half blue/half white is a carrier with normal vision, but one abnormal gene.

Karyotypes Process in which cells undergoing mitosis are crushed, and their chromosomes paired up. This can reveal abnormalities as seen below. Female – 2 X chromosomes

Nondisjunction The failure of chromosomes to separate during anaphase I or II of meiosis. Can result in too many chromosomes (Down Syndrome) or not enough (Turner Syndrome)

Autosomal Dominant Diseases If the abnormal gene is present, the person has the disease Huntington’s Disease

Huntington’s Disease Chromosome 4 HH or Hh Nerve cells degenerate Symptoms include: mood swings, irritability, loss of memory, and uncontrolled movements People of western European descent

Autosomal Recessive disease Must have 2 abnormal forms of the gene for the disease to be present Cystic Fibrosis Tay Sachs PKU (Phenylketonuria) Sickle Cell Anemia

Cystic Fibrosis Chromosome 7 cc Causes think, sticky mucus to build up in the lungs, digestive tract, and other areas of the body Mainly Caucasians

Tay Sachs Chromosome 15 tt Causes a buildup of a chemical on the nerve cells Babies lose or fail to gain motor and mental skills Paralysis usually occurs Death at an early age Jews of eastern European descent and French-Canadians

PKU Chromosome 12 pp Born without the ability to break down phenylalanine Smaller than normal head, epilepsy, and mental retardation may occur when undiagnosed Caucasians and east Asians

Sickle Cell Anemia Chromosome 11 ss Red blood cells form an abnormal crescent shape Pain; spleen, lung, and heart damage, and anemia People of African descent

Sex-linked Diseases Gene for the disease is carried on the sex-chromosome Colorblindness Hemophilia

Colorblindness Carried on the X chromosome XbXb or XbY Cannot distinguish between colors Affects all races and ethnic groups

Hemophilia Carried on the X chromosome XhXh or XhY Blood does not clot well because missing the gene that codes for a blood clotting protein Affects all races and ethnic groups

Chromosomal Aneuploidy Diseases A disease caused by an abnormal number of chromosomes Down Syndrome Turner’s syndrome Kleinfelter’s syndrome XYY Male

Down’s Syndrome Autosomal anueploidy Trisomy (three chromosomes at 21) Mental retardation, upward slant to the eyes, decreased muscle tone, and a variation of other symptoms

Turner’s Syndrome Sex chromosome anueploidy Monosomy Alters development in females; shorter than average, infertile, extra skin on the neck, skeletal abnormalities, heart defects, and kidney problems

Kleinfelter’s Syndrome Sex chromosome anueploidy Trisomy (XXY) Armpit and facial hair, enlarged breasts, tall stature, and abnormal body proportions Increased possibility of learning disorders

XYY Male Sex chromosome anueploidy Trisomy (XYY) Increased risk of learning disabilities, delayed speech and language skills