Human+Genetics+2+hw-+kat

=__Human Genetics__=

Define:

 * 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

==Describe diseases (You will need to know how they are inherited ie X-linked recessive or autosomal dominant. You will also need to know the gene that is mutated and what damage that causes to the body)==


 * 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.