Genetics+Questions+SLS

November 13, 2008 Science-Human Bio**
 * Shelby Smith


 * Genetics Questions**


 * Chapter 20 Patterns Of Genetic Inheritance**
 * 1. Define genotype, alleles, dominant allele, recessive allele, homozgous dominant, homzygous recessive, heterozygous, phenotype**
 * Alleles**: alternative forms of genes having the same posistion on a chromosome and affecting the same trait
 * Dominant**: assigned the uppercase letter. if there is a dominant gene then the baby will get the dominant trait.
 * Recessive**: assigned the the losercase. you would need to only have recessive to have the recessive trait. any dominant and the trait is automatically dominant.
 * Homozygous Dominant**: two uppercase alleles or two dominant alleles.
 * Recessive**: two recessive alleles
 * Heterozygous**: one dominant and one recessive allele
 * Phenotype**: physical appearance of someone

A genotype refers to the genes of the individual, while on the other hand the phenotype is that physical appearance of the individual.
 * 2. What is the difference between genotype and phenotype?**

Ee, ee, and EE. These phenotypes and genotypes are concerned with the earlobes.
 * 3. What are the three possible genotypes and the two possible phenoyptes for a characteristic that is controlled by two alleles, one being dominant and the other recessive?**


 * 4. Write down the question and answer for questions 1,2,3 on page 423.**

a.WW: WW b. WWss: Ws Ws c.Tt: Tt d. Ttgg: Tg Tg tg tg e.AaBb: AB Ab aB ab
 * 1.) For each of the following genotypes, give all possible gametes: WW, WWss, Tt, Ttgg, AaBb**

a.D: gamete b.Ll: genotype c.Pw: genotype d.LlGg:gamete 3. what is the genotype of the individual from the following crosses a.EeSs b.SSee
 * 2.) For each of the following, state whether a genotype or a gamete is represented.**


 * 5. Define the following genetic disorders on pp. 431 to 432 Make sure you describe the function of the gene that is mutated and what happens with the mutated gene.**


 * Taysachs disease:** Tay-sachs disease is awell known autosomal recessive disorder that occurs usually among Jews. It is the lack of the enzyme hexosaminidase A (Hex A) . Lysosomes build up in many body cells, but the primary sites of storage is in the brain, which account for the onset of symptoms and the progressive deterioration of psychomotor functions. The baby is fine till four to eight months and then the baby gradually becomes blind and helpless, develops uncontrollable seizures and eventually becomes paralyzed.


 * Cystic fibrosis:** This is also autosomal recessive, and it is most common lethal genetic disorder among whites. Chloride ions fail to pass through a plasma membrane channel protein in the cells of the patients. Then, this would be the lack of water and which would cause abnormally thick mucus to build up in bronchial tubes and pancreatic ducts. This build up of mucus then interferes with the function of the lungs and pancreas.


 * Phenylketonuria:** Phenylketonuria is an autosomal recessive metabolic disorder that affects nervous system development. Affected individuals lack an enzyme that is needed for the normal metabolism of the amino acid phenylalanine, and therefore, it appears in the urine and the blood. Newborns are routinely tested in the hospital for elevated levels of phenylalanine in the blood. If elevated levels are detected, newborns will develop normally if they are placed on a diet low in phenylalanine, which must be continued until the brain is fully developed, around the age of seven, or else severe mental retardation develops. Some doctors recommend that the diet continue for life, but in any case, a pregnant woman with phenylketonuria must be on the diet in order to protect her unborn child from harm.


 * Sickle-cell disease:** Sickle-cell disease is an autosomal recessive disorder in which the red blood cells are not biconcave disks like normal red blood cells; they are irregular. In fact, many are sickle-shaped. The defect is cause by an abnormal hemoglobin that differs from normal hemoglobin by one amino acid in the protein globin. The single amino acid change causes hemoglobin molecules to stack up and form insoluble rods, and the red blood cells become sickle-shaped. Because sickle-shaped cells can’t pass along narrow capillary passageways as disk-shaped cells can, they clog the vessels and break down. This is why persons with sickle-cell disease suffer from poor circulation, anemia, and low resistance to infection. Internal hemorrhaging leads to further complications, such as jaundice, episodic pain in the abdomen and joints, and damage to internal organs. Sickle-cell heterozygotes have sickle-cell traits in which blood cells are normal unless they experience dehydration or mild oxygen deprivation. Still, at present, most experts believe that persons with sickle-cell trait do not need to restrict their physical activity.


 * Marfan Syndrome: **Marfan syndrome, an autosomal dominant disorder, is cause by a defect in an elastic connective tissue protein, called fibrillin. This protein is normally abundant in the lens of the eye; the bones of limbs, fingers, and ribs; and also in the wall of the aorta. This explains why the affected person often has a dislocated lens, long limbs and finger, and a caved-in chest. The aorta wall is week and can possibly burst without warning. A tissue graft can strengthen the aorta, but Marfan patients with aortic symptoms still should not overexert themselves.


 * Huntington’s disease**: Huntington disease is a neurological disorder that leads to progressive degeneration of brain cells. The disease is caused by a mutated copy of the gene for a protein, called huntingtin. Most patients appear normal until they are of middle age and have already had children, who may later also be stricken. Occasionally, the first sign of the disease will appear during the teen years or even earlier. There is no effective treatment, and death comes 10 to 15 years after the onset of symptoms. Several years ago, researches found that the gene for Huntington disease was located on chromosome 4. A test was developed for the presence of the gene, but few people want to know it they have inherited the gene because there is no cure. At least now we know that the disease stems from a mutation that cause the huntingtin protein to have too many copies of the amino acid glutamine. The normal version of huntingtin has stretches of between 10 and 25 glutamines. If huntingtin has more than 36 glutamines, it changes shape and forms large clumps inside neurons. Even worse, it attracts and causes other proteins to clump with it. One of Researchers hope they may be able to combat the disease by boosting CBP levels.