A copy of a gene whose effect is only observed when it is homozygous.
An allele which is not expressed unless two copies are present in the individual, i.e., in homozygous condition.
the phenotype that only shows up in the offspring if the dominant allele is not inherited.
An allele whose phenotype is not expressed in a heterozygote.
The allele that only appears as a trait when both copies are in its form.
a gene that is expressed only when its counterpart allele on the matching chromosome is also recessive (not dominant). Autosomal recessive disorders develop in persons who receive two copies of the mutant gene, one from each parent who is a carrier. (See Dominant allele.)
an allele which will only result in a specific phenotype when its counterpart allele is also recessive, or when no counterpart allele exists. "Autosomal recessive disorders" develop in individuals who inherit two mutant copies of a gene which is located on one of the autosomes. When a recessive gene associated with disease occurs on certain parts of the X chromosome, the disease (hemophilia is an example) is known as an "X-linked recessive disorder." X-linked recessive disorders may occur more often in men than in women, because men inherit only one copy of the gene (since they have only one X chromosome).
A form or mutation of a gene that must be inherited from both parents to produce a trait or disease.
An allele whose phenotypic effect is not expressed in a heterozygote.
Allele whose characteristics do not tend to be expressed when part of a heterozygous genotype. Its genetic characteristics tend to be masked by other alleles.
