Complex Inheritance Patterns Flashcards
what is Mendel’s rules correct for? what don’t they work for?
correct for predicting genotype, but not for most phenotypes and traits
define incomplete dominance
where neither allele completely dominates and you get a “blended” phenotype
what does incomplete dominance reflect the importance of?
important of gene dosage in creating most phenotypes
describe multiallelic genes
for most genes in diverse populations, there are almost always more than just two alleles
example of multiallelic gene
tyrosinase- a tissue specific effector gene that encodes an enzyme required for melanin synthesis (there are 102 functional mutations - phenotypic alleles - of the mouse tyrosinase gene in exons and CREs
describe pleiotropic genes, what rule does it defy?
mutations in a single gene affects many “traits”, defies the “one gene, one trait” rule
describe continuous phenotypic variation
very few traits are “binary” like simple mendelian genetic diseases, most phenotypes fall on a broad spectrum
potential causes of continuous phenotypic variation
1) CRE mutations that create partial LOF or GOF alleles with slight more/less expression
2) mulitgenic traits where several genes add together to give phenotype
3) environment contributes to variation
example of “multigenic trait”
height- multiple intercellular signaling receptors/ligands, T.F.s and tissue specific effector genes work together to determine height
the only “exception” to Mendel’s rules relating to genotype and alleles
genetic linkage, genes are not physically independent particles
what does genetic linkage predict? who observed this?
predicts that certain phenotypes will tend to appear together, Thomas Hunt Morgan saw linkage using vinegar flies (probably because he looked at many more traits than Mendel)
why does genetic linkage happen?
genes can be physically linked on chromosomes and as a result, alleles and phenotypes can co-segregate
linkage in practical terms
phenotypes for body color, eye color, and wing shape would usually occur together and defy independent assortment ratios seen by Mendel
why is linkage not usually complete?
because crossing over can “unlink” alleles & the further apart two genes are on a chromosome, the higher the odds of crossing over happening between them and then they behave more like “independently assorting” particles predicted by Mendel
describe sex determination
whether germline cells differentiate into eggs, sperm, both or neither
