Chapter 8: Identification of Semen
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Typical ejaculation
 2-5 ml of semen, 160 million sperm
▪ 3 pg DNA/sperm = 480,000 ng DNA/ejaculate
▪ Only 1 ng DNA needed for STR typing!
 Seminal fluid
▪ Seminal vesicle fluid- 60% of ejaculate
▪ Prostatic fluid secretions- 30% of ejaculate
▪ Acid Phospahatase (AP) & Prostate Specific Antigen (PSA)
▪ Epididymis and bulbourethral glands- each 5%
 Sperm cells- Spermatozoa
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Not all semen stains contain sperm
 Vasectomy- block spermatozoa
▪ Still produces ejaculate with seminal vesicle fluid and
prostatic fluid
▪ Will not have enough sperm for DNA typing
 Oligospermia- low sperm count
▪ May or may not have enough sperm for DNA typing
 Aspermia- no sperm
▪ Will not have enough sperm for DNA typing
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Three distinct regions:
 Head – acrosome and nucleus (with haploid DNA)
 Middle Piece (mitochondria)
 Tail (flagella; mobility)
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Optimal activity in acidic pH environment
Present in lysosomes
Prostate is most abundant source of AP
Half-life at 37 degrees C: 6 months
AP levels not affected by vasectomy
High levels in blood serum can be a sign of
prostate cancer
See Lecture 5 for specifics of AP spot test
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Major protein in seminal fluid
Also detected in urine, fecal matter, sweat,
milk but in much smaller quantities
Half-life of dried stain: 3 years
Hydrolyzes semenogelins (seminal vesicle
specific antigens)
 Semenogelins causes semen to form gel following
ejaculation
 Hydrolyzing semenogelin keeps the semen fluid
during ejaculation
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Semenogelins
 I & II
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Higher concentration in seminal fluid than
PSA
Not found in urine, milk, sweat
 Greater specificity for semen than PSA
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Lighting methods (ALS)
Presumptive tests
 Colorimetric
 Fluroimetric
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Confirmatory tests
 Microscopy for spermatozoa
 Antigen-antibody interactions
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Locating dried stains
 UV light (long-wave =
“Woods Lamp”)
 Argon laser
 Alternate light source
(ALS)
▪ 450-495 nm
▪ BLUEMAXX (in lab)
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AP catalyzes the removal of the phosphate
group from a substrate
Positive= purple color
See Lecture 5
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More sensitive than colorimetric
AP catalyzes the removal of the phosphate
residue on the substrate 4methylumbelliferone phosphate (MUP),
which generates fluorescence under UV light
Filter paper overlay
 Filter paper placed in contact with putative semen
stain and then removed and taken to dark room
 Sprayed with MUP
 Fluorescence detected with UV lamp
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Microscopic examination
 Christmas Tree Stain
 Stains sperm heads red and sperm tails green
Acrosomes don’t stain well
in primate sperm
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Identification of prostate-specific antigen
Older methods:
 Radial immunodiffusion
 Rocket immunoelectrophoresis
 CIE
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Current method
 Imunnochromatographic assay
▪ Most sensitive
▪ See Lecture 5 for details on PSA immunochromatography
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