DNA Forensics Problem Set 1

Problem 4: Rape investigation


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

Samples of DNA were loaded into the following lanes:

  1. known blood sample of victim
  2. known blood sample from defendant
  3. DNA size markers
  4. female fraction from vaginal swab of victim
  5. male fraction from vaginal swab of victim.
If you are the DNA analyst, you should conclude that:

A. The suspect is guilty
B. The suspect might be guilty, but more probes should be used.
C. The vaginal swab is from the wrong victim.
D. The suspect is excluded as a source of DNA in the evidence.
The top band in lane 5 (the male fraction from vaginal swab) does not match any bands in lane 2 (the defendant's known sample), excluding him as a contributor of that DNA.
E. NONE of these.

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