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FRNSC 421W - EXAM 2-Questions with Correct Answers/ Verified/ 100% Pass
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FRNSC 421W - EXAM 2-Questions with Correct Answers/ Verified/ 100% Pass
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FRNSC 421W - EXAM 2-Questions with Correct Answers/ Verified/ 100% PassDNA mixtures - ✔️✔️mixed biological fluids/cells of any type
- saliva & skin cells
- blood & semen
- urine from two sources
- sexual assault cases often contain female epithelial/white blood cells & male sperm,
epithelial/white blood cells
characteristics of sperm - ✔️✔️- condensed nucleus in the head, encapsulated by acrosome
- mid-piece with ~50 (range from 10-1300) copies of mitochondrial DNA
- tail composed of motile flagellum, allows for quick swimming (~25 µm/s or 30 inch/hr)
anterior acrosomal sac (AAS) - ✔️✔️tip of the sperm head, encompasses by plasma membrane
(PM) and outer acrosomal membrane (OAM)
- where hydrolytic (hyaluronidase) and proteolytic (acrosin) enzymes are found
hyaluronidase - ✔️✔️found in the AAS, lowers the viscosity of hyaluronic acid in the interstitial
barrier of the egg through hydrolysis
- hyaluronic acid is a "goo" acting as a lubricant in many cell types, allows for increased access to
unfertilized egg cell
acrosin - ✔️✔️digestive enzyme in AAS, assists with the breakdown of proteins in the unfertilized
cell membrane
acrosome reaction - ✔️✔️during fertilization, a sperm fuses with the plasma membrane and
penetrates the female egg cell to fertilize it
- membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head
- with no AAS, the nuclear membrane and DNA in nucleus is exposed and hyaluronidase + acrosin is
released
- this allows the egg to be fertilized; the egg surface conditions are changed, blocking other sperm
from entering
- spermicidal foams/jellies block reaction w/o destroying DNA; condoms act as a barrier entirely
- mtDNA produces ATP, used by tail as energy to move
, sexual assault statistics - ✔️✔️- approx. 1 in 6 women will become victims
- the majority of perpetrators are white males
- >100,000 cases per year in US, only ~2000 cases result in convictions (~1 in 10)
- conviction allows for low recidivism; if you catch a suspect early, will reduce # of victims
types of SA evidence - ✔️✔️- swabs: generally have multiple sources of DNA (oral, vaginal, anal,
etc.)
- slides: confirm presence of sperm
- pubic combings: roots (nDNA) or shaft (mtDNA) of hair for microscopy or DNA analysis
- articles of clothing: use ALS for stains
influences on finding sperm - ✔️✔️- vasectomy/low sperm count
- minimal ejaculation
- urination
- vaginal pH
- contraceptives
- bathing or washing with harsh detergents (bleach)
survival of sperm - ✔️✔️- in vaginal cavity, ~72 hours to 7 days
- in anal cavity, ~24 hours to 3 days
- in oral cavity, ~6-24 hours
H&E staining - ✔️✔️hematoxylin (aka hemalum, or aluminum/hematoxylin) and eosin
- used to stain sperm cells on slides
- H is a basic dye, binds to acidic tissue (DNA/RNA) to stain nuclei blue/purple color
- E is an acidic dye, binds to basic tissue as a red/pink color
Christmas tree stain - ✔️✔️confirmatory stain for sperm cells on slides
- nuclear fast red/aluminum sulfate stains the sperm heads
- picroindigocarmine dye stains tails green
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