Lectures 8-9 Flashcards
2 postulates of gene transmission
1) genes are present on HC
2) chromosomes segregate and assort independently
what is the ultimate source for new alleles?
mutations!!!
loss-of-function mutations
mutation causes loss of WT function
gain-of-function mutations
mutation enhances WT function; quality of gene product increases
neutral mutations
no change to the phenotype; does not affect evolutionary fitness
LOF mutations result in…
the gene being partially or fully inactive
LOF functions are often but not always…
recessive
if loss is complete then the mutation results in…
null allele
GOF mutations cause…
enhanced activation of gene or its products
GOF mutations are usually…
dominant
dominant-negative mutations
mutant allele acts antagonistically to wild type allele
incomplete or partial dominance results in…
intermediate phenotype with neither allele being dominant
codominance
two alleles of single gene produce two gene products; joint expression in heterozygotes
essential genes are absolutely required for…
survival
a gene is considered essential when…
loss of its function compromises the viability or fitness of the organism
recessive lethal alleles result in…
homozygous recessive individuals and do not survive
dominant lethal allele
only one copy of allele is needed to cause death
epistasis
multiple genes come together to contribute to a specific phenotype
dominant epistasis (A)
dominant allele at one loci masks an allele at second loci
recessive epistasis (aa)
when a recessive allele on one gene masks the effects of another gene
complementation analyses
test to determine whether mutations are on same or different genes
pleiotropy
expression of single gene has multiple phenotypic effects
penetrance
percentage of expression of mutant genotype in population
expressivity
range of expression of mutant phenotype
conditional mutations
temperature affects phenotype
extranuclear inheritance
inheritance patterns which vary from traditional biparental inheritance of nuclear genes
