Pedigree of families with low penetrance and mosaic <i>RB1</i> mutations.

<p>Family <b>F1</b>: Father is a normal carrier of the heterozygous mutation: c.607+1G>T; Altered splicing. The proband and his younger brother carry the same heterozygous mutation and have unilateral RB. The proband also had an elder deceased sibling. Family <b>F2</b>: Father is an unaffected carrier of the heterozygous mutation: c.1981C>T; p.Arg661Trp. The proband and his brother have bilateral RB and carry the same heterozygous mutation. Family <b>F3</b>: The proband with unilateral RB carries a homozygous mutation: c.940-1G>C (altered splicing) in tumor. Only 4% of the proband’s blood leukocytes tested positive for the mutation (mosaicism). Both parents tested negative for the given mutation. Family <b>F4</b>: The proband with unilateral RB carries a homozygous mutation: c.958C>T; p.Arg320* in tumor. Only 2% of the proband’s blood leukocytes tested positive for the given mutation (mosaicism). Both parents tested negative for the given mutation. Family <b>F5</b>: The proband with unilateral RB has a deletion of one copy of <i>RB1</i> allele in tumor and a mosaicism for the same mutation in blood, as only 60% blood leukocytes carried the given mutation. Both parents tested negative for the given mutation. Genotype is provided for tested members as m/m for homozygous carriers, m/+ for heterozygous carriers and +/+ for homozygous wild-type. Blackened symbols: bilateral RB; half-blackened symbols: unilateral RB; diagonally blackened symbol: Unknown Laterality of RB; dotted symbols: unaffected carriers; dashed symbols: deceased.