Expression of a recessive (nondominant) trait, which occurs only if the offspring receives identical recessive alleles from both parents. (44)
A pattern of inheritance of a characteristic (such as blue eye color) or abnormality (such as congenital absence of the vas deferens) in which two abnormal genes or alleles are needed to confer the characteristic or abnormality, in contrast to dominant inheritance, which requires just one abnormal gene. In the case of alleles found on X-chromosomes but not on the smaller Y-chromosomes, a recessive gene will be unopposed (and so will act as a dominant gene) in males, whereas female carriers of the allele will be unaffected except in the extremely unlikely event that they inherit (or gain by mutation) a second abnormal allele; this mode of inheritance is called sex-linked recessive inheritance. See also: homozygous
mutation has to be inherited from both parents in order for a person to be affected. Such parents are usually unaffected carriers because they only have a single copy of the mutant gene.
A mode of genetic inheritance whereby an affected person must have two dysfunctional forms of the gene to have the disease.
The situation in which inheritance of the same poorly functional or abnormal gene from both parents results in the expression of a syndrome or disease in the offspring. (That is, two copies of the poorly functional or abnormal recessive gene are required for the syndrome or disease to be expressed.)
With autosomal recessive inheritance, the diseased individual has inherited the same gene damage from both father and mother. The damage is found on both chromosomes in the pair. But as this is not ´dominant gene damageª, neither father nor mother show any sign of disease, they are healthy carriers of the gene. We are all carriers of about five recessive genes of this type, but as spouses are seldom carriers of exactly the same damaged gene(s), all will probably go well in the next generation.
