What is true of genetic diseases with variable expression?
The nature and severity of the phenotype varies from one individual to another with the same disease
What is true of genetic diseases with incomplete penetrance?
Not all individuals with the mutant genotype will show the complete mutant phenotype
What is the significance of imprinting in genetic diseases?
A genetic disease has a different phenotype depending on whether the mutation is inherited from the mother or from the father
What is meant by linkage disequilibrium?
Measured in a population, it is the tendency for certain alleles at two linked loci to occur together more often than expected by chance
What term describes the situation in which cells in the body have a different genetic makeup?
What is the name of the phenomenon whereby a genetic disease has an earlier onset or worsening severity in each subsequent generation?
What word describes the phenomenon of a single gene having more than one effect on an individual's phenotype?
Prader-Willi and Angelman syndromes are the result of which genetic process?
The random inactivation of one X chromosome in females
A patient has inherited a mutation in a tumor suppressor gene. Mutation of the remaining (previously normal) copy of the tumor suppressor gene represents a loss of _____, which may lead to the development of cancer.
Heterozygosity; the patient was previously a heterozygote for lost tumor suppressor gene and both genes must be lost for oncogenesis
True or False? Oncogenes, in a manner similar to tumor-suppressor genes, must have a deletion/mutation in the complementary allele before cancer develops.
False; the mutation of a single oncogene can produce cancer
A genetic disease that shows _____ _____ will have mutations at different loci that produce the same phenotype.
True or False: Albinism is an example of a genetic disease that demonstrates locus heterogeneity.
What is an example of a genetic disease that displays anticipation?
The presence of both normal and mutated mitochondrial DNA, resulting in variable expression in mitochondrial inherited diseases
What is the significance of a dominant negative mutation?
A nonfunctional altered protein that also prevents the normal gene product from functioning
Name a disease whose pathogenesis involves loss of heterozygosity.
The tendency for certain alleles to be inherited together more often than is expected by chance is called what?
True or False? The Hardy-Weinberg law assumes that there are no mutations at the locus being studied.
What equation describes the disease prevalence in a population that is in Hardy-Weinberg equilibrium?
p2 + 2pq + q2 = 1; where q2 is the prevalence of an autosomal recessive disease
What is the heterozygote prevalence in a population that is in Hardy-Weinberg equilibrium?
In Hardy-Weinberg population genetics, what do p and q represent?
Alleles of a gene
What are the four assumptions of the Hardy-Weinberg equation?
No mutation occurring at the locus; no selection for any of the genotypes at the locus; completely random mating; no migration
The prevalence of which type of genetic disease is indicated by q in males and q2 in females in Hardy-Weinberg genetics?
X-linked recessive diseases
How is Prader-Willi syndrome inherited?
It is inherited via the deactivation of paternal copies of genes on chromosome 15
In genetics, what does the term imprinting refer to?
When, at a single locus, one allele is inactivated by methylation (an inherited condition) and one allele is not (disease occurs as the result of the loss of the active allele)
How is Angelman syndrome inherited?
Via the deactivation of the maternal copies of genes on chromosome 15; via chromosomal deletion, faulty imprinting, or uniparental disomy
Where is the gene located in Prader-Willi syndrome? In Angelman's syndrome?
Both syndromes are due to inactivation or deletion of genes on chromosome 15
What are the signs of Prader-Willi syndrome?
Mental retardation, obesity, hypogonadism, and hypotonia
What are the signs of Angelman's syndrome?
Mental retardation, seizures, ataxia, and inappropriate laughter (happy puppet syndrome)