Genetic Heterogeneity

Example of Phenocopy

Drugs can lead to birth defects that seem to be a genetic disorder (HIV infection)

Example of Penetrance AND Expressivity

HUNTINGTON's: Two genes interacting can cause Huntington's Second gene can increase stem cells where Huntington affects the brain = decreases progression of Hunt (b/c stem cells fix things) = delay of Hunt. (so Huntington will be NON PENETRANT)

EX of Genetic Heterogeneity

Leber Congenital Amaurosis : many ways a mutation can disrupt the functioning of the rods and cones

Example of Epistasis AND Genetic Heterogeneity

MARFAN SYNDROME: - symptoms can be caused by another gene that is mutated and on the same biochemical pathway (genetic heterogeneity) - If fibrillin (what those w/ Marfan are defect in) is WT and there is an alternate (not mutated or WT) form of TGFBR gene that can dominantly overtake fibrillin and can cause the same symptoms as Marfan (epistasis)

How are mitochondrial genes and diseases inherited?

MATERNALLY

Heteroplasmy

Presence of both normal and mutated mtDNA, resulting in variable expression in mitochondrial inherited disease - mitochondria is in the same cell having different alleles for a particular gene -chances of passing on are complex and unpredictable b/c at cell division, segregation is random (could have more WT or more mutated type)

How are mutated mitochondria related to cell division?

Random segregation can cause some daughter cells to get a lot of good and/or a lot of bad mutated mitochondria takes time and chance for it to have an effect

Genetic Heterogeneity

a phenotype that can be caused by variants of any of several genes (mutations that cause one phenotype) * different than compound heterozygote*

Phenocopy

an environmentally caused condition has symptoms and a recurrence pattern similar to those of a known inherited trait