1. Pedigree of a familial retinoblastoma case that shows no evidence of meiotic recombination. Closed symbols = bilaterally affected family members; half-closed symbols = unilaterally affected members; open symbols = unaffected members. Arrows indicate the family member for whom diagnosis before illness was performed; the indications of the presence or absence of disease are based on subjects' status at their most recent ophthalmic examination. Inferred alleles at the retinoblastoma (RB1) locus are designated rb for a mutant allele and + for a wild-type allele. The circles with vertical lines below them that are shown under each family member symbol represent the member's two constitutional chromosome 13 homologues. The numbers beside each chromosome symbol represent the allelic form of each locus. The vertical order of loci within each family is the same as that shown under the symbol for its I-1 member. The data illustrate the power of information about a first child in discriminating which chromosome a second child has inherited from the affected parent. (Reprinted from Cavenee et al., New England Journal of Medicine, vol. 314, pp. 1201–1207, 1986, by permission.)
Source: Retinoblastoma, The Online Metabolic and Molecular Bases of Inherited Disease
Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular Bases of Inherited Disease; 2014 Available at: Accessed: October 20, 2017
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