Mendel's Laws Applied to Complex Traits
Over dominance
- A type of dominance characterized by a phenotype that is more pronounced in a heterozygote relative to that of the counterpart homozygote - The heterozygous exceeds the phenotypic measurements of the homozygous parents.
Lethality
A condition in which the inheritance of a lethal combination of alleles results in death of the organism
Schizophrenia
A disorder that's highly heritable and often shows a pattern of anticipation. It affects a person's mood and how she views herself and the world.
Internal environment
Age, sex limited, sex controlled or sex influenced, Substrates
Twin Studies
Carried out in humans using identical twins, fraternal twins and non-twin siblings reared apart and together
Incomplete dominance
In this case dominance is absent and the progeny does not resemble any of its parents.
Recessive lethals
Lethal genes whose phenotypic effects are ordinarily recessive have no observable phenotypic effect in the heterozygous but produce a noticeable and eventually lethal change in homozygous recessive
Epigenetics
One of the biggest challenges to Mendel's laws comes from this phenomenon. In this, the organisms organisms with identical alleles (including identical twins) may exhibit different phenotypes.
polydactyly
One trait with variable expressivity that shows up in humans, condition of having more than ten fingers or toes.
Expressivity
Regardless of penetrance, the degree to which an allele expresses the phenotype may differ from individual to individual; this variable strength of a trait is
Anticipation
Sometimes, traits seem to grow stronger and gain more expressivity from one generation to the next. The strengthening of a trait as it's inherited
External environment
Temperature, light, nutrition, maternal relations,
Dominant epistasis
There is complete dominance at both gene pairs, but one gene, when dominant, masks the effect of the other. e.g. fruit color in summer squash
Novel Phenotype
There is complete dominance in both gene pairs
Duplicate Genes
There is complete dominance in both gene pairs, but either gene, when dominant, is epistatic to the other.
Complementary genes
There is complete dominance in both gene pairs, but either recessive homozygote is epistatic to the effects of the other gene.
Recessive epistasis
There is complete dominance in both gene pairs, but one gene, when homozygous recessive, hides or masks the effect of the other.
Dominant lethals
These are genes whose lethal effects occur when a dominant allele is present in a homozygous or heterozygous condition e.g. epiloia in human results in abnormal skin growths, severe mental defects and multiple tumors, causing early deaths; Huntington's disease
Co dominance
When alleles share equally in the expression of their phenotypes, the inheritance pattern is considered as this
Incompletely penetrance
When dominant alleles are present but fail to show up as a phenotype, the condition is termed as this
Pleiotropy
a situation in which one gene has multiple phenotypic effects
Concordant
both members show the character
yellow coat color in mice.
first lethal allele that scientists described was associated with
Discordant
if only one member of a pair shows the trait
Phenocopy
it means an environmental mimic of gene action
Complete penetrance
means every person having the allele shows the phenotype.
Penetrance
refers to the proportion of genotypes that show an expected phenotype. It is a statistical concept of the regularity with which the gene is expressed
Epistasis
sometimes genes hide or mask the action of other genes altogether
Expressivity
the degree to which a particular phenotypic effect is expressed by the individual
Lewis Effect or Poison Effect
the phenotype was determined not only by the genotype but also by the position of the different alleles on the chromosome
penetrance
the probability that an individual having a dominant allele will show the associated phenotype.
Simple dominance
when the dominant allele's phenotype, or physical trait masks the presence of the recessive allele.
