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.
allele. [ÉlÄlâ²]. 1 one of two or more alternative forms of a gene that occupy corresponding loci on homologous chromosomes. Each allele encodes a phenotypic feature or a certain inherited characteristic. An individual normally has two alleles for each gene, one contributed by the mother and one by the father.