extensions of Mendelian Inheritance Flashcards
wild type alleles
most prevalent version of a gene in wild populations in which the proteins function normally and promote reproductive success of an organism
in large populations, there may be more than 1 common allele considered wild-type
polymorphism- inheritance of a trait controlled by a single genetic locus with 2 alleles
mutant alleles
are less common version of a gene that can be due to random mutations that occur in DNA or due to mutations induced by scientists
difference between wild-type and mutant alleles
Wild-type is the normal phenotype of an organism found in natural populations, whereas mutant alleles have an abnormal phenotype that differs from the normal.
3 types of dominant alleles
gain of function, dominant negative, and haplo-insufficiency
penetrance
proportion of individuals that have a specific allele as well as the associated phenotype
incomplete penetrance
when an allele does not completely penetrate into the population
Ex: 40% penetrant allele = 40% of pop. with allele will show phenotype, where are the other 60% will NOT show phenotype but will carry allele
incomplete dominance
form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele, results in a third phenotype of a combination of the phenotypes
Ex: red flower (R1R1 ) x white flower (R2R2) = pink flower (R1R2)
codominance
multiple alleles being expressed, each allele encodes a functional protein but in a different sequence
Ex: ABO blood type in humans
overdominance
where a heterozygote produces a phenotype more extreme/better adapted than that of the homozygote
Ex: sickle cell anemia, heterozygotes have a higher resistance to malaria and sickle cell than their homozygous counterpart
incomplete dom. vs. codominance vs. over dominance
incomplete is a mixture of the 2 alleles, codominance when both alleles are expressed together in offspring, and overdominance is when the heterozygote phenotype is better than their homozygous counterpart.
how can the 2 protein variants produce a favorable phenotype in the heterozygote?
disease resistance, homodimer formation, variation in functional activity
sex-influenced traits
when an allele is dominant in 1 sex, but recessive in the next
Ex: male patterned baldness
sex limited traits
are traits that occur in only one 1/2 of the sexes, both sexes have genes. Is responsible for sexual dimorphism
lethal alleles
is a mutation in an essential gene leading to a non-function protein product leading to a lethal phenotype
essential genes
are genes that are necessary for an organism
conditional lethal alleles
exert effects only under certain conditions
Ex: drosophila are temperature sensitive, large will not survive under certain temp
semi-letal alleles
can cause death of individuals with the affected genotype, however not all will die
pleiotropy
when single gene has multiple effects on the phenotype of an organism
why does pleiotropy happen?
gene product has multiple uses in cellular function, gene is expressed in different cell types, or the gene is expressed during different stages of development
epistasis
inheritance pattern in which allele of 1 gene masks the phenotypic effects of the alleles of a different gene
Ex: Lab coat color
complementation
2 different parents that express the same or similar recessive phenotypes produce offspring with a wild-type genotype
modifying genes
phenomenon in which an allele of 1 gene modifies the phenotypic outcome of the alleles of a different gene
gene redundancy
pattern in which the loss of function in a single gene has no phenotypic effect, but loss of function of 2 genes has an effect
extranuclear inheritance
inheritance pattern of traits not in nuclear genes (genes where DNA is located in the cell nucleus)
how are chloroplasts and mitochondria inherited
are commonly inherited from the female parent (via edge cells)
genomic imprinting
imprinted genes express one allele (maternal or paternal), the other is silenced.
recessive alleles
typically produce less function proteins, proteins tend to be defective and the organism produces lower levels of that functional protein
dominant alleles
effect phenotype with just one copy, they are less common in natural systems
