SectionIIC Flashcards
What are the characteristics of an autosomal dominant inheritance pattern?
- no skipped generations
- father-to-son transmission (rules out X linked)
- at least one parent affected
- both sexes affected
What are the recurrance rate of autosomal dominant and recessive traits?
- Dominant= 50%
- Recessive= 25%
How does a new mutation complicate an autosomal inheritance pattern?
- Becuase the disease occurs with no prior family hisotry
- child of offsping has increased risk
- parents of the affected do not have an increased risk becuase their germline is typically normal
What is germline mosaicism?
- When all or part of a parent’s germline is affected by a disease mutation but the somatic cells are not affected.
- Therefore the parent has no signs but there is an elevated risk for recurrance in the offspring
What is reduced penetrane and what is the example given?
- a person who has a disease causing genotype but not the phenotype.
- retinoblastoma
What is age-dependent penetrance?
-A disease which does not manifest until later in life, once the carrier has had children.
E.g. Huntington disease
What factors influence variable expression?
- modifier loci
- allelic heterogenicity
- environmental factors
What is pleitropy?
- genes that have more than one discernable affect on the body
- like Marfan Syndrome
What is heterogenicity?
- A single disease phenotype that is caused by mutations at different loci in different families
- like adult polycystic kidney disease
What is genomic imprinting?
-Some genes are expressed exclusively on paternally or maternally transmitted chromosomes.
What is the theory of repeat expansion?
-in deaseses cause by repeats, as mor repeats are passed down, the **disease is more likely to manifest or manifest earlier. **
What is consanguinity?
- Mating between relitives
- increases the frequency of genetic disease, especiall rare recessive disorders.
