Chapter20+Genetics+HW7+MC

Chapter 20 Genetics SCI Human Biology - 1 Assigned: 11/13 Due: 11/17 Chapter 20 Patterns Of Genetic Inheritance 1. Define genotype, alleles, dominant allele, recessive allele, homozgous dominant, and homozygous recessive, heterozygous, phenotype -Genotype: genes of an individual for a particular trait or traits; often designated by letters. -alleles: alternative form of a gene; alleles occur at the same locus on homologous chromosomes. -dominant allele: allele that exerts its phenotypic effect in the heterozygote; it masks the expression of the recessive allele. -recessive allele: allele that exerts its phenotypic effect only in the homozygote; its expression is masked by a dominant allele. -homozygous dominant: possessing two identical alleles, such as AA for a particular trait. -homozygous recessive: Possessing two identical alleles, such as aa, for a particular trait. -heterozygous: possessing unlike alleles for a particular trait. -phenotype: visible expression of a genotype –for example, brown eyes or attached ear lobes. 2. What is the difference between genotype and phenotype? - The genotype is the gene of an individual for a particular trait or traits; often designated by letters. A phenotype is the visible expression of a genotype –for example, brown eyes or attached ear lobes. 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? -3 possible genotypes are homozygous dominant, homozygous recessive, and heterozygous. Two possible phenotypes are brown eyes or attached earlobes. 4. Write down the question and answer for questions 1,2,3 on page 423. -1) For each of the following genotypes, give all possible gametes; a) WW= not possible because no two letters in a gamete can be the same letter of the alphabet. b) WWSs= SW, Ws c) Tt= not possible because no two letters in a gamete can be the same letter of the alphabet d)Ttgg= Tg, gt e) AaBb= AB, aB, Ab, ab -2) For each of the following, state whether a genotype or a gamete is represented. a) D= gamete b) Ll= Genotype c) Pw= gamete d) LlGg=genotype -3) What is the genotype of the individual from the following crosses? a) ES x es =EeSs, unattached earlobes and short fingers b) eS x eS = eeSS, short fingers and attached earlobes 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.
 * Tay-sachs disease- a well known autosomal recessive disorder that occurs usually among Jewish people in the United States, most of whom are of central and eastern European descent. Lysosomes build up in many blood cells of the brain, which accounts for the onset of symptoms and the progressive deterioration of psychomotor functions. Development begins to slow down between four and eight months of age, and neurological impairment and psychomotor difficulties then become apparent. The child gradually becomes blind and helpless, develops uncontrollable seizures, and eventually becomes paralyzed.
 * cystic fibrosis- an automosal recessive disorder that occurs among all ethnic groups, but it is the most common lethal genetic disorder among Caucasians in the United States. Cystic fibrosis is due to a faulty protein that is supposed to regulate blood flow of chloride ions into and out cells through a channel protein. The mutated gene makes the lungs infected frequently and you would have clogged pancreatic ducts preventing digestive enzymes from reaching the small intestine. It’s hard to breathe too, but to ease breathing the thick mucus in the lungs has to be manually loosened periodically.
 * phenylketonuria-an autosomal recessive metabolic disorder that affects nervous system development . affect 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.
 * sickle-cell disease- an autosomal recessive disorder in which the red blood cells; they are irregular. The cells clog the vessels and break down. It’s caused 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 rolds, and the red blood cells become sickle-shaped.
 * marfan Syndrome- an autosomal dominant disorder, is caused by a defect in 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 has a dislocated lens, long limbs and fingers, and a caved-in chest.
 * huntingtons's disease- a neurological disorder that leads to progressive degeneration of brain cells. This disease is caused by a mutated copy of the gene for a protein, called Huntington. Researchers found that it’s located on chromosome 4. The disease stems from a mutation that causes the Huntington protein to have too many copies of the amino acid glutamine. The normal version of Huntington has stretches between 10 and 25 glutamines. If Huntington 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.