In the inherited form of retinoblastoma, an affected child is heterozygous for an rb mutation, which is ei-ther passed on from a parent or has newly arisen in the sperm or the oocyte nucleus that gave rise to the child. The heterozygous RB / rb cells are nonmalignant, how-ever. The RB allele of the heterozygote must be knocked out in the developing retinal tissue to create a tumorous cell. Such a knockout can occur through an independent mutation of the RB allele or by mitotic crossing-over such that the original rb mutation is now homozygous. a. If retinoblastoma is passed on to other siblings as well, could we determine whether the original mutation was derived from the mother or the father? How? b. Could we determine whether the rb mutation was maternally or paternally derived if it arose de novo in a germ cell of one parent? Solution a. If the trait is inherited, we can determine from which parent it came. The most straightforward approach is to identify DNA polymorphisms, such as restriction frag-
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.