Title: Pedigrees and Modes of Inheritance - Biology Encyclopedia - cells, plant, body, examples, function, human, different, chromosomes
Headings: Pedigrees and Modes of Inheritance
Pedigrees and Modes of Inheritance
Phenotype, Genotype, and Alleles
Pedigree Symbols
Modes of Inheritance
Autosomal Dominant
Autosomal Recessive
X-linked
Mitochondrial
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Content: In autosomal recessive inheritance, both alleles are  mutant. Parents of affected individuals are unaffected carriers. heterozygous for this mutation and thus unaffected carriers. Each of the  parent's offspring has a 25 percent chance of inheriting the  illness and a 75 percent chance of being unaffected. However, of the  latter, two-thirds will be heterozygous like their parents, and one-third  will be homozygous for the normal gene and thus cannot pass on the trait. An autosomal recessive trait or disease may occur in individuals of both  sexes. People with homozygous mutations are frequently the product of a consanguineous marriage (Figure 3). A recessive disease can, however, also be caused by  two different mutations in the same gene (more frequent in nonconsanguineous  marriages), which are then called compound heterozygous mutations. X-linked
An X-linked trait is carried on the X chromosome. In pedigrees depicting  X-linked inheritance, usually only males are affected and, although  affected males may occur in consecutive generations, transmission is  always through females.