14 Autosomal Disorders Flashcards
what are the two mendel’s principles?
segregation -> two copies of a gene with an equal chance of one going to offspring
independent assortment -> each gene inherited does not affect any other gene no matter how related
what are the two rules of probability
multiplicative -> probability of several events occurring together -> overall risks is multiplication of each event’s risk
additive rule -> probability of one event occurring vs another in a set -> overall risks is the sum of all risks which will all add to one
what is the differences between genotype and phenotype
genotype is the genetic make up
phenotype is the results compounded by external influences
what are features of autosomal dominant disorders?
only need one allele for expression but homozygotes have extreme symptoms
usually one affected parent with one allele-> 50% offspring risk
relatively rare but does not skip generations
no sex linked pattern -> father to son possible = rule out x linked
give examples of a autosomal dominant disorders
retinoblastoma, postaxial polydactyly, achodroplasia
what are features of autosomal recessive disorders
requires homozygous alleles for phenotype
heterozygous alleles result in carrier
two carriers result in 25% affected and 50% carrier
skips generations
cosanguinity compounds risk
give examples of autosomal recessive disorders
albinism
cystic fibrosis -> disrupted chloride transport -> clogs pancreatic duct and lungs -> also excess chloride in sweat
how can a disorder be both dominant and recessive?
more than one gene takes part in the disease pathway
What are three incidences when new mutations can be suspected?
inheritance not following an expected pattern (esp auto dominant or x-linked)
parents of child confirmed biological parents and are homozygous normal
explain germline mosaicism
when only a portion of a germline cell (ie embryonic cell) mutates and the individual has only a portion of affected cells
mutants are usually x linked or auto dominant
what are two factors considered when considering odd phenotype expression
delayed onset -> age a factor -> may have passed down genes as well
incomplete penetrance -> modifying genes may reduce, exacerbate or abolish phenotype
what disease shows variable expression
neurofibromatosis is auto dom but some get few skin lesions while others get large numerous tumors
- lesions called cafe au lait spots
what is pleiotropy and what two categories do they originate from?
one gene able to affect many tissues
DNA transcription factors or extracellular matrix proteins
give an example of a pleiotropic gene caused disorder
Marfans syndrome affecting bone/cartilage structure as well as cardiac structure
explain the two forms of heterogenicity and give examples
allelic heterogenicity -> one gene -> multiple mutant forms
ie. thalassemias, sickle cell
locus heterogenicity -> multiple genes -> one pathway -> similar disorder with different genes
ie. most urea cycle disorders
