Chapter 11, Problem 26P

Scientists were surprised to discover recently that marmosets, a kind of monkey, are often chimeric—they have cells that originated from two different zygotes. Marmoset chimeras occur in fraternal twins. While in their mother's womb, these twins can share cells through the blood supply because their placentas are fused. Any organ or tissue, including the germ line, can be chimeric. To determine if a particular male fathered any of four baby marmosets from three different mothers, DNA fingerprinting of four SSR loci was performed using genomic DNA from hairs. In the accompanying diagram, the thickness of the bands correlates with the amount of DNA present. You can use the dots on both sides of the diagram, along with a ruler or paper edge, to help compare the positions of the bands.

a.	What is the maximum number of different alleles of any one SSR locus that the hair cells of any one marmoset could have?
b.	Which of the four babies could have been fathered by the male whose DNA fingerprint is shown?
c.	Identify the pair of chimeric fraternal twins.
d.	Does any evidence exist for chimerism in the father of the twins? in the mother?
e.	Explain how the biological mother of a baby marmoset can be its genetic uncle. (Note: This is not necessarily the situation for any of the baby marmosets in the figure.)