HB+Human+Genetics+2

=Human Genetics 2=

__terms__

 * Carriers:**
 * heterozygous individual who has no apparent abnormality but can pass on an allele for a recessively inherited genetic disorder
 * Autosomal recessive disorder:**
 * when the child is affected, but neither parent is affected.
 * Autosomal dominant disorder:**
 * when the child is affected because the parents are affected.
 * Autosomes:**
 * any chromosome other than the sex chromosomes
 * Sex chromosomes:**
 * chromosome the determines the sex of an individual, in humans females have two X chromosomes males have an X and Y chromosomes.
 * Sex linked:**
 * allele that occurs on the sex chromosomes but may control a trait that has nothing to do with the sex characteristics of an individual.
 * X linked:**
 * allele located on an X chromosome, but may control a trait that has nothing to do with the sex characteristics of an individual.
 * X linked dominant:**
 * when males pass the trait //only// to daughters.
 * X linked recessive:**
 * more males then females are affected, an affected son can have parents who have the normal phenotype

__diseases__

 * Tay-sachs:**
 * a well known autosomal recessive disorder that usually occurs among Jewish people, results from a lack of the enzyme hexosaminidase A (Hex A) and the storage of its substrate, a glycosphingolipid in lysosomes. Development begins slow, usually 4-8 months of birth, child becomes gradually blind, helpless, uncontrollable seizures, and becomes paralyzed.
 * Cystic Fibrosis:**
 * an autosomal recessive disorder occurs among ethnic groups, chloride ions fail to pass through a plasma membrane channel protein in the cells of patients. Causes built up of mucous in bronchial tubes and pancreatic ducts.
 * PKU:**
 * an autosomal recessive disorder that affects nervous system development, affected individuals lack an enzyme that is needed for the normal metabolism of the amino acid phenylalanine.
 * Sickle Cell Disease:**
 * an autosomal recessive disorder in which the red blood cells are not bioconcave disks like normal red blood cells. Leads to poor blood circulation.
 * Mafan Syndrome:**
 * an autosomal dominant disorder, caused by a defect in an elastic connective tissue protein, called **fibrillin**.
 * Huntington Disease:**
 * an autosomal dominant disorder, a neurological disorder that leads to progressive degeneration of brain cells. Disease is caused by a mutated copy of the gene for a protein called **huntingin**.
 * Color blindness:**
 * X-linked recessive disorder, see brighter greens as tans, olive greens as browns, and reds as reddish browns.
 * Muscular dystrophy:**
 * X-linked recessive disorder characterized by wasting away of the muscles. The absence of the protein dystrophin is the cause of muscular dystrophy.
 * Hemophilia:**
 * X-linked recessive disorder, Hemophilia A is due to the absence or minimal presence of a clotting factor or known as factor VIII, hemophilia B is due to the absence of clotting factor IX. Its called a bleeding disease because blood doesn't clot or clots slowly.