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.
Share. By Regina Bailey. Definition: An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. These DNA codings determine distinct traits that can be passed on from parents to offspring through sexual reproduction.he dominant allele is expressed and the recessive allele is masked. This is an example of complete dominance. In heterozygous relationships where neither allele is dominant but both are completely expressed, the alleles are considered to be co-dominant. Co-dominance is exemplified in AB blood type inheritance.