unit 11-blood spatter and serology Flashcards
Proteins found on the surface of red blood cells are called
antigen
Phenolphthalein is used to determine the presence of ___ by its reaction with ____.
Blood:hemoglobin
CODIS stands for______.
combined DNA index system
What is the correct set of antigen/antibody found in the blood types A, B, AB, and O?
blood type A: A: anti-B
blood type: B: B: anti A
blood type: AB: AB: none
blood type: O: none: anti A or anti B
Luminol is used to detect ___ by _____
Detect blood by chemiluminescence
What procedures and materials are used in the forensic analysis of semen?
- Visual examination
- Alternate light source: light source with control over wavelength in the Ultraviolet, infrared and visible range
- Acid phosphatase test : a presumptive color test for semen
- Prostate specific antigen (PSA) test: conformity test for semen
- Microscopic sperm search
What are the problems with mitochondrial DNA (mtDNA) analysis in identifying a specific individual?
- Not as specific as nuclear DNA (is identical to all family members of a maternal line)
- They are indistinguishable
Define the area of convergence and area of origin and explain what each reveals to an investigator.
- The area of convergence is the point on a two-dimensional plane from which the drops of an impact spatter pattern originated. It determines the area/location from which the blood originated
- The area of origin of a bloodstain pattern is the area in three-dimensional space where blood projected from, showing the position of the victim or suspect
A destructive protein found in the blood serum is called
antibody
What are the following factors that are used as a basis for the assessment of the evidence?
(l) Is it blood? (2) From what species did the blood originate? (3) If the blood is human, how
closely can it be associated with a particular individual?
Compare a Polymerase Chain Reaction to a Short Tandem Repeat.
- polymerase chain reaction (PCR)—A technique for replicating or copying a portion of a DNA strand. Can amplify minute quantities of DNA
- short tandem repeat (STR)—A region of a DNA molecule that contains short segments of three to seven repeating base pairs.
What are the possible concerns with DNA evidence collection?
- Mixture: If sample has more than one individual contributing to create a mixture , can be hard to separate the specific alleles
- Degradation: DNA can degrade due to environmental factors (heat and humidity)
How can pools of blood aid in reconstructing a crime scene?
Pools of blood can aid in reconstruction because the drying time of the blood can provide an estimation of the amount of time that has elapsed since the blood was deposited.
Give a description of the shape of blood droplets on porous and nonporous surfaces.
- Hard, nonporous surfaces will produce circular stain patterns that have smooth edges
- Softer, porous surfaces will produce spatter stains that are scalloped or have rough edges.
calculate impact angle formula
sin(-1)= width/length
What are the three steps needed for DNA extraction?
- Lysis
Cells are broken open or lysed, using mechanical and chemical means. The cell wall, cell membrane, and
nuclear membrane must all be disrupted to release the DNA. (the nucleus and cell are broken up) - purification
Once cells are broken open, the entire cellular contents are mixed. Most manipulations of DNA require the
DNA to be free of proteins and RNA. - precipitation and concentration
DNA is soluble in water and insoluble in alcohol
- removes all the remaining cellular debris and unwanted material
Depending on the type of surface that is impacted by blood spatter during a crime, the blood droplet can form satellites which can change the overall design of the evidence. These droplet satellites are _________
Satellite spatter (Small droplets Of blood that are distributed around the perimeter of a drop or pool of blood and were produced as a result of the blood impacting the target surface.)
