non-mendelian inheritance- lecture 11 Flashcards
Mendelian inheritance
- For every gene, there are two alleles
- Of these two alleles, one allele is dominant to the other, which is recessive
Incomplete dominance
is a kind of non-Mendelian inheritance where, instead of two alleles
having a dominant and recessive relationship to each other, neither allele is dominant or
recessive. Instead of heterozygotes having the phenotype associated with one dominant allele,
they instead express an intermediate phenotype
Codominance
sounds pretty similar to incomplete dominance, and the two are easily confused
for each other. But whereas traditional dominance/recessiveness involves a dominant allele masking a recessive allele, and incomplete dominance involves the amount of protein being
made, codominance is about co-expression of two different phenotypes
Incomplete penetrance
Easily confused with incomplete dominance, since they both have the word “incomplete” right
there at the beginning, incomplete penetrance occurs when a phenotype associated with a
genotype does not always occur
Variable expressivity
Variable expressivity is actually quite different from incomplete penetrance. With variable
expressivity, it’s not about whether or not you express the phenotype associated with your
genotype–it’s about the degree to which you express a phenotype, or the ways that you
express it.
lethal alleles
will cause deviations from expected mendelian ratios
multiple alleles
provide a greater number of possible genotypes/phenotypes than just 2 alleles
multiple alleles example
human blood groups
complete vs codominance vs incomplete dominance
In complete dominance, only one allele in the genotype is seen in the phenotype. In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype
complete dominance
Complete dominance is a condition wherein the dominant allele completely masks the effect of the recessive allele; consequently, both alleles must be recessive for the recessive allele to be expressed.
polygenic
many genes contribute to the expression of one trait (skin color, height)
pleoptropy
one gene has an effect on many traits (cystic fibrosis)
epistasis
Epistasis is a circumstance where the expression of one gene is modified (e.g., masked, inhibited or suppressed) by the expression of one or more other genes (genes work together)
epistasis problem
sex influenced traits
autosomal genes can be expressed differently in males and females
Sex-influenced traits are autosomal traits that are influenced by sex. If a male has one recessive allele, he will show that trait, but it will take two recessive for the female to show that same trait. One such gene is baldness
sex limited traits
Sex-limited traits are traits that are visible only within one sex. For instance, barred coloring in chickens normally is visible only in the roosters
maternal genetic effect
In genetics, maternal effects occur when an organism shows the phenotype expected from the genotype of the mother, irrespective of its own genotype,
maternal genes whose products, RNA or protein, are produced or deposited in the oocyte or are present in the fertilized zygote
name some characteristics of cytoplasmic inherited traits
not all genes are encoded in the nuclear chromosomes
genetic imprinting
an allele is differentially expressed, depending on whether it is inherited from the male or female parent
maternal effect gene
mother supplies mrna or protein to the egg that is essential for development
genetic maternal effect
direction of turning of shell
genotype says shell should turn toward the left because that is dominant but because the mother is ss and recessive, they turn to right because genotype of mother determines phenotype of offspring
mitochondrial diseases
lhon
mitochondrial replacement therapy
environmental effects: temperature sensitive allele
allele whose product is functional only at certain temperatures
environmental effects: maternal environment
environment of mother can influence offspring genotype
