Assume that defects in a hypothetical gene, X, have been linked to antisocial behavior. Two copies of a defective gene X predispose a child to bad behavior from childhood, while a single copy of the gene seems to produce no symptoms until adulthood. Since the effects of the gene can be counteracted if treatment is started early enough, a program of voluntary genetic testing is being carried out with delinquent prospective parents. Charles S. and Caril Ann F. have been arrested on charges of robbery and assault, and Caril Ann is pregnant with Charles’s child. You obtain DNA samples from Charles, Caril Ann, and the fetus. You digest these samples with Not I and use these samples to perform two Southern Blots, which you probe with two different oligonucleotide probes, A and B, that hybridize to different parts of the normal gene X, as shown in Figure Q10-9A. Your results are shown in Figure 10-9B.
A. Which of the three individuals have defects in gene X?
B. Which individuals have a single defective gene and which have two defective copies of the gene?
C. Indicate the nature (single base-pair mutation or deletion) and location of each individual’s defects on gene X.
Figure Q10-10 shows a restriction map of a piece of DNA containing your favorite gene. The arrow indicates the position and orientation of the gene in the DNA. In part B of the figure are enlargements showing the portions of the DNA whose sequences have been used to make oligonucleotide probes A, B, C, and D. Which of the oligonucleotides can be used to detect the gene in each of the following?
A. A Southern blot of genomic DNA cut with Hind III.
B. A Northern blot.