extensions of mendelian inheritance pt.2 Flashcards
A heterozygotes possess a phenotype that is intermediate between the homozygous dominant and homozygous recessive phenotypes. This is an example of?
incomplete dominance
in four-o’clock plants, red flower color is dominant to white flower color. However, heterozygous plants have pink flowers. If a pink- flowered plant in crossed with a white flowered plant, what will be the phenotypic ratios of their offspring?
1/2 pink, 1/2 white
in human blood groups, the fact that an individual can have an AB blood type is an example of
codominance
An individual with type A blood and an individual with type B blood mate and have offspring. What is the only blood type can you be certain is possible in their offspring?
type AB blood
epistasis is
when one gene can mask the expression of a second gene
sickle cell anemia in humans is an example of
overdominance/ heterozygote advantage
which term refers to the situation where the effects of one gene mask the phenotype effects of another gene
epistasis
the multiple effects of a single gene on the phenotype of an original is called
pleiotropy
polymorphism
in large populations there may be more than one common allele
why are mutants recessive?
- 50% of normal levels of protein are enough for full function
- the one wild-type copy is up-regualted in expression, to produce adequate amount of functional protein
dominant alleles
alleles that effect phenotype as just one copy
Gain-of-function mutation (dominant allele)
gene gains a new/abnormal function
dominant-negative mutations
mutant protein acts to antagonize normal protein
haploinsufficiency
mutant is a loss of function allele and one wild type copy is not enough to provide function
why are recessive mutant alleles typically produce less functional protein
because the protein is defective or they produce lower levels of the functional protein
incomplete penetrance
an allele does not always “penetrate” into the phenotype of the individual
penetrance
population of a chromosome carrying the dominant allele and exhibiting the trait
what causes incomplete penetrance and variable expressivity
- the environment may affect the outcome of the trait
2. there may be modifier genes that affect the phenotype
norm of reaction
range of phenotypes seen across different environmental effects
overdominance / heterozygote advantage
when a heterozygote is more vigorous than the 2 homozygotes
ex: sickle cell anemia
explanation for overdominance at the molecular/cellular level
- disease resistance
- homodimer formation
- variation n functional activity
heterosis ( hybrid vigor)
out-crossing; cross-pollinating species
codominance
both alleles are expressed
ex: blood type
sex-influenced traits
an allele is dominant in one sex but recessive in the other
sex-limited traits
traits that occur only in one of the two sexes
essential genes
genes required for survival
lethal allele
an allele with the potential to cause death, usually due to a result in the mutation of an essential gene
temperature sensitive conditional lethal allele
temperature sensitive proteins mis-fold at higher temps, becoming nonfunctional
conditional lethal allele
an allele that can kill an organism only under certain environmental conditions
gene redundancy
existence of multiple genes in the genome of an organism that performs the same function
gene dosage
number of copies of a particular gene present in the genome
multiple allele system
type of non-mendelian pattern that involves more than typical 2 alleles that code for certain characteristics
complementation
relationship between 2 different strains of an organism which both have homozygous recessive mutations that produce same phenotype
expressivity
how affected an individual may be to mutation
