Ap Bio Diseases Research
CHAPTER 14 1. Norm of reaction: the phenotypic range that a genotype is associated with due to environmental influences. 2. Multifactorial: characters that have many factors, both genetic and environmental, collectively influence phenotype. 3. Pleiotropy: when a gene controls multiple phenotypic effects 4. Epistasis: When a gene at one locus alters the phenotypic expression of a gene at a second locus 5. Carrier: a person who is heterozygous for a recessive disease and therefore does not display the phenotype (disease). They are called carriers because although they are phenotypically normal with regard to the disorder, they can transmit the recessive allele to their offspring. They are heterozygotes and normal (Rr)
DISEASES
a. Recessively Inherited Disorders
Tay-Sachs disease * Inherited disorder in humans where the brain cells of a child with the disease cannot metabolize certain lipids because a crucial enzyme does not working properly. * As the lipids accumulate in the brain cell, the child beings to suffer seizures, blindness, and degeneration of motor & mental performance and dies within a few years. * Only children who inherit two copies of Tay-Sachs allele (HOMOZYGOUS) have the disease. Therefore at the organismal level, the Tay Sachs allele qualifies as recessive * The intermediate phenotype observed at the biochemical level is characteristic of incomplete dominance of either allele * At the molecular level, the normal allele and the Tay-Sachs allele are codominant because a person heterozygous for Tay Sachs disease does not have the disease symptoms, but the individual still produces equal number of normal and dysfunctional enzyme molecules
Cystic Fibrosis * Most common lethal genetic disease in the U.S, strikes one out of every 2,500 people of European descent. * The normal allele for this gene codes for a membrane protein that functions in the transport of chloride ions between certain
DISEASES
a. Recessively Inherited Disorders
Tay-Sachs disease * Inherited disorder in humans where the brain cells of a child with the disease cannot metabolize certain lipids because a crucial enzyme does not working properly. * As the lipids accumulate in the brain cell, the child beings to suffer seizures, blindness, and degeneration of motor & mental performance and dies within a few years. * Only children who inherit two copies of Tay-Sachs allele (HOMOZYGOUS) have the disease. Therefore at the organismal level, the Tay Sachs allele qualifies as recessive * The intermediate phenotype observed at the biochemical level is characteristic of incomplete dominance of either allele * At the molecular level, the normal allele and the Tay-Sachs allele are codominant because a person heterozygous for Tay Sachs disease does not have the disease symptoms, but the individual still produces equal number of normal and dysfunctional enzyme molecules
Cystic Fibrosis * Most common lethal genetic disease in the U.S, strikes one out of every 2,500 people of European descent. * The normal allele for this gene codes for a membrane protein that functions in the transport of chloride ions between certain