8/25/14 - Patterns of Single Gene Inheritance Flashcards
What is consanguinity?
The genetic relationship that results from common ancestry. The more closely related 2 individuals are, the more likely they are to share alleles from a common ancestor.
How is mitochondrial DNA inherited?
Maternally
What are some characteristics of sex-linked recessive inheritance patterns?
-Affected fathers transmit disease to their grandsons through their daughters -All daughters of affected fathers are carriers -Female carriers have a 50% chance of transmitting the diseased allele to their children
What are some characteristics of sex-linked dominant inheritance patterns?
-Affected fathers always transmit the disease to their daughters but never their sons -Female carriers have a 50% of transmitting the *disease* to their children
What is penetrance?
The proportion of individuals possessing a mutant gene who exhibit clinical symptoms. In other words, not all individuals with a mutant allele will show disease symptoms.
What is the coefficient of inbreeding?
1/2 x coefficient of relationship
What are two examples of hemizygosity?
-Deleted gene results in only one copy at a given locus -Sex-linked genes in males
Which gene, UBE3A or SNRNP, would you expect to be methylated in a patient with Angelman syndrome?
UBE3A. In AS, the deletion occurs on the maternal chromosome, leaving only the silenced paternal UBE3A. Since the patient inherited a healthy chromosome 15 from the father, you would expect SNRNP to be unmethylated/active.
What is heteroplasmy?
There is more than one type of DNA in a cell. Ex. mitochondrial DNA
What is hemizygosity?
Only possessing a single allele at a given locus.
What is variable expressivity?
A difference in the severity of disease among patients with the same genotype. In other words, two individuals may have the same disease-causing allele, but one individual has far worse symptoms.
What are some characteristics of autosomal dominant inheritance patterns?
-Phenotype is seen in heterozygotes -Males/females equally affected -Unaffected family members are unlikely to transmit the disease
What is a compound heterozygote?
Individual who has 2 different mutant alleles at a given locus.
What is the proband?
The first affected family member who seeks medical attention for a genetic disorder.
What are the seven complications seen in basic inheritance patterns that lead to non-Mendelian inheritance?
- De novo mutations 2. Genomic imprinting 3. Reduced penetrance 4. Variable expressivity 5. Phenotypic variability 6. Delayed onset 7. Small family size
What are some characteristics of autosomal recessive inheritance patterns?
-Only homozygotes affected -Males/females equally affected -Parents are carriers
What are 4 classic symptoms of Prader-Willi syndrome?
- Hypogonadism 2. Mental retardation 3. Obesity 4. Hyperphagia
What is incomplete dominance?
The phenotype resulting from a heterozygous genotype is distinct and often intermediate. Ex. red, *PINK*, white flowers
What are the characteristics of Angelman syndrome? Include specific gene affected and imprinting pattern (not symptoms)
-Maternal UBE3A allele normally active, paternal allele normally silenced -In AS, maternal UBE3A is lost due to deletion, only silent paternal UBE3A is left -Most cases caused by deletion on Q-arm of chromosome 15
What are 4 general features of mitochondrial DNA diseases?
- Maternal inheritance 2. Reduced penetrance 3. Variable expressivity 4. Pleiotropy
What is anticipation?
Genetic abnormalities worsen in subsequent generations. Common in tri-nucleotide repeat expansion disorders such as Huntingtons.
How do you determine the degree of relationship?
Count the number of uninterrupted lines in a pedigree map that relate 2 family members
What is the coefficient of relationship?
(1/2)^n, where n is the degree of the relationship
What is haploinsufficiency?
One normal allele is insufficient to compensate for the loss of the other.
