Genetic Basis of Complex Inheritance Flashcards
What are the 3 laws of mendelian inheritance?
Dominance
Segregation
Independent Assortment
What mechanisms cause incomplete penetrance?
Environmental
Genetic modifiers
What mechanisms cause genomic imprinting?
Variants from parents
What mechanisms cause extranuclear inheritance?
Mitochondria mutations
What mechanisms cause anticipation?
Triplet repeat expansion.
Define penetrance.
Frequency with which a trait is manifested by individuals carrying the gene.
What is the penetrance of cystic fibrosis?
100%
What is the penetrance of breast cancer?
70-80%
What is allele frequency?
The variation of alleles in a population.
What is cystic fibrosis caused by?
Mutation in CFTR (Autosomal recessive).
What is the prevalence in european caucasians?
1 in 2500
What two phenotypes are variable in cystic fibrosis?
Severity
Affected organs
What builds up in cystic fibrosis?
Mucus
What are genetic modifiers?
Genes that have small quantitative effects on the level of expression of another gene.
What are included in environmental factors?
Lifestyle Diet Smoke Alcohol Drug Stress Air pollution
What does polymorphism mean?
May occur in different forms, i.e cystic fibrosis can have different forms which is why it affects people differently.
What are the 4 features of genetic factors?
Rare
Simple
Uni-factorial
High recurrence
What are the 4 features of environmental factors?
Common
Complex
Multi-factorial
Low recurrence
What is genomic imprinting?
Genes expressed from only one chromosome.
What is genomic imprinting dependent on?
Parent-of-origin.
What are epigenetic modifications?
Heritable changes in gene function which can’t be explained by changes in DNA sequences.
What are deletions, point mutations, imprinting errors and uniparental disomy examples of?
Genetic mechanisms
Why do imprinted genes have a higher risk of disease?
Expression is only from a single copy
What is uniparental disomy?
Inheritance of a chromosome pair from one parental origin.
