Mr. I. M. Megabucks, the wealthiest man in the world, recently died. Since his death, three women have come forward. Each woman claims to have a child by Megabucks and demands a substantial share of his estate for her child. Lawyers for the estate have insisted on DNA typing of each of the alleged heirs. Fortunately, Megabucks anticipated trouble like this before he died, and he arranged to have a sample of his blood frozen for DNA typing.
Remember that every person has two of each chromosome, one inherited from his mother and one inherited from his father. Half of every person's DNA comes from his mother, and half comes from his father, so some of the DNA bands showing on the gels of the children will come from their mothers, and the rest will come from their fathers. The question is, could that father be Megabucks?
For the first child, identify the DNA bands that came from the mother. (Remember: not all of the mother's DNA is passed to the child; just one of each pair of chromosomes.) Mark the bands that came from the mother with an M. Circle the remaining bands.
Compare the remaining (circled) bands with Megabucks’ DNA. If he is the father, then all of the circled bands for the child's should have a corresponding band in his profile. Use a straightedge to help you line up the bands. Remember: only half the father's chromosomes are transmitted to a child, so not every band from the father would match the child's profile (but every band on the child that doesn’t match the mother, must match the father).
Repeat the analysis for the other alleged heirs. Could any of them be Megabucks' children?
On a separate sheet of binder paper, record whether each child could belong to Mr. Megabucks, or definitely could not belong to him AND give the following proof:.
To prove a child COULD belong to Megabucks, you must list each band (by its size in base pairs) and match it to an identical band in either the mother or Megabuck’s lane.
To prove a child does NOT belong to Megabucks, you must identify at least one band for the child that does NOT match its mother OR Megabucks.