DNA Forensics Problem Set

DNA Forensics Problem Set 2

Problem 7: Rape with Two Suspects

Correct!

The key portion of the autoradiograph from a single locus probe analysis of various DNA samples in a rape investigation is shown in the figure.

The DNA samples are as follows:

(1) known blood sample of victim
(2) known blood sample from Suspect A
(3) known blood sample from Suspect B
(4) DNA size markers
(5) female fraction from sexual assault evidence
(6) male fraction from sexual assault evidence.

If you are the DNA analyst, you should conclude that:

A. Both Suspects A and B are excluded as the source of the evidence.

B. Suspect A is excluded as the source of the evidence, but Suspect B cannot be excluded.

C. Suspect B is excluded as the source of the evidence, but Suspect A cannot be excluded.
Because both bands of Suspect A match those found in the male fraction of the sex assault evidence, A cannot be excluded as a source of the DNA. However, because Suspect B has no matching bands with the male fraction of the vaginal swab, Suspect B can be excluded.

D. Neither Suspect A or B can be excluded as a source of the evidence.

E. Suspect B cannot be excluded as a source of the evidence. The results with Suspect A are inconclusive.

The Biology Project
University of Arizona
Tuesday, August 20, 1996
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