Chapter 10, Problem 20P

Microarrays were used to determine the genotypes of seven embryos (made by in vitro fertilization) with regard to sickle-cell anemia. Each pair of squares in the accompanying figure represents two ASOs, one specific for the Hbβ^A allele (A) and the other for the HBβ^s allele (T), attached to a chip of silicon and hybridized with fluorescently labeled PCR product from a single cell from one of the embryos. The hybridizations were performed at three different temperatures (80°C, 60°C, and 40°C) as shown.

a.	Why do you think the PCR step is needed for this microarray analysis?
b.	Make a sketch of the location in genomic DNA of the PCR primers relative to the sickle-cell mutation. Indicate the 5′-to-3′ polarities of all DNA molecules involved.
c.	Why is no hybridization seen at 80°C?
d.	Why do you see strong hybridization of all genomic DNA probes to both ASOs at 40°C?
e.	What are the genotypes of the seven embryos? Which of these embryos would you choose to implant into the mother’s uterus to avoid the possibility that the child would have sickle-cell anemia?