Income Exclusion Rule. DEFINITION of 'Income Exclusion Rule'. A rule that sets aside certain types of income as nontaxable. There are many types of income that qualify under this rule, such as life insurance death benefit proceeds, child support, welfare and municipal bond income. Income that is excluded is not reported anywhere on Form 1040.
Ancestral vs derived alleles. An ancestral allele or an ancestral trait (depending on whether you look at the phenotype or a t the genotype) is the trait/allele that was carried by the common ancestor of the taxon you consider.
You will recall that genes have different forms called alleles. An allele can be recessive or dominant. A recessive allele only shows if the individual has two copies of the recessive allele. For example, the allele for blue eyes is recessive.You need two copies of the allele to have blue eyes.A dominant allele always shows, even if the individual only has one copy of the allele. For example, the allele for brown eyes is dominant. You only need one copy of the allele to have brown eyes (and two copies will still give you brown eyes).or example, the allele for blue eyes is recessive. You need two copies of the allele to have blue eyes. A dominant allele always shows, even if the individual only has one copy of the allele.