Chapter 13, Problem 31P

Fred and Mary have a child named Bob. The genomic DNAs of these three individuals are used as probes to ASO microarrays such as that shown in Fig. 11.17. The results with 10 SNP loci (1–10) located along chromosome 21 are shown in the figure that follows. Yellow, orange, and red indicate increasing intensities of hybridization.

a.	Is Bob likely to have Down syndrome? Explain.
b.	Do the data provide evidence that a nondisjunction event occurred in one of the parents? If so, in which parent and during which meiotic division?
c.	Do the data provide evidence that a recombination event occurred during meiosis in either parent? If so, in which parent, and describe the approximate location of the crossover.
d.	Describe how this example illustrates why it is important when tracking nondisjunction events to look particularly at loci near the centromere.