Title: Hereditary Diseases | Article about Hereditary Diseases by The Free Dictionary
Headings: Hereditary Diseases
Hereditary Diseases
Hereditary Diseases
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Content: Pathological heredity can be traced horizontally in the family genealogy. The probability of children being born with hereditary disease increases if the parents are blood relatives. A genealogy characteristic of the autosomal-recessive type of disease is shown in Figure 2. Figure 2. Autosomal-recessive type of inheritance
If one of the parents is homozygous for a pathological recessive gene and the other is its heterozygous carrier, then children with hereditary disease may be born in half the cases. This creates the impression of a dominant type of hereditary disease (a genealogy is shown in Figure 3). This phenomenon is called pseudodominance. Pseudodominance differs from true dominance in that affected individuals homozygous for a recessive mutation when married to healthy persons will always have healthy offspring, but heterozygous, apparently healthy persons when married to other heterozygous carriers will have diseased children with a certain frequency (25 percent). If the genealogy shown in Figure 3 is traced back one more generation, it will look like that in Figure 4. Figure 3.