Non-medelian inheritance Flashcards
what is penetrance?
the frequency with which a trait is manifested by individuals carrying the gene
what is the penetrance of cystic fibrosis?
~100%
what are the mechanisms of non-mendelian inheritance?
- incomplete inheritence
- genomic imprinting
- extranuclear inheritance
- anticipation
what can alter prevalence?
- genetic modifiers
genes that have small quantitative effects on level of expression of another gene - environmental factors
eg. lifestyle, diet, smoking, alcohol, stress, air pollution, chemicals infection (for cystic fibrosis)
what is genomic imprinting?
genes on chromosomes inherited from may be switched on or off depending on which parent they are inherited from
how does the inactive of genes in genomic imprinting occur?
methylation
mechanisms for when genomic imprinting affects an individual
deletions (of only active gene) point mutations (in active gene) imprinting errors uniparental disomy
what is uniparental disomy?
inheritance of a chromosome pair from one parent only
examples of conditions caused by imprinting disorders
Angelman syndrome
Prader-Willi syndrome
what causes Angelman syndrome?
loss of a maternal gene from the q section of chromosome 15
what causes Prader-Willi syndrome?
loss of a paternal gene from the q section of chromosome 15
what is mitochondrial disease?
the inherited disease is not due to mutations in the nuclear but in the mitochondral DNA
what is anticipation?
a disease presents at earlier age and /or increasing severity in succeeding generations
what is complex inheritance?
characteristics are encoded by multiple loci
what is incomplete inheritance?
when one allele is not completely dominant over another
