unit 11-blood spatter and serology

Question 1

Proteins found on the surface of red blood cells are called

Answer 1

antigen

Question 2

Phenolphthalein is used to determine the presence of ___ by its reaction with ____.

Answer 2

Blood:hemoglobin

Question 3

CODIS stands for______.

Answer 3

combined DNA index system

Question 4

What is the correct set of antigen/antibody found in the blood types A, B, AB, and O?

Answer 4

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

Question 5

Luminol is used to detect ___ by _____

Answer 5

Detect blood by chemiluminescence

Question 6

What procedures and materials are used in the forensic analysis of semen?

Answer 6

• 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

Question 7

What are the problems with mitochondrial DNA (mtDNA) analysis in identifying a specific individual?

Answer 7

• Not as specific as nuclear DNA (is identical to all family members of a maternal line)
• They are indistinguishable

Question 8

Define the area of convergence and area of origin and explain what each reveals to an investigator.

Answer 8

• 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

Question 9

A destructive protein found in the blood serum is called

Answer 9

antibody

Question 10

What are the following factors that are used as a basis for the assessment of the evidence?

Answer 10

(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?

Question 11

Compare a Polymerase Chain Reaction to a Short Tandem Repeat.

Answer 11

• 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.

Question 12

What are the possible concerns with DNA evidence collection?

Answer 12

• 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)

Question 13

How can pools of blood aid in reconstructing a crime scene?

Answer 13

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.

Question 14

Give a description of the shape of blood droplets on porous and nonporous surfaces.

Answer 14

• 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.

Question 15

calculate impact angle formula

Answer 15

sin(-1)= width/length

Question 16

What are the three steps needed for DNA extraction?

Answer 16

1. 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)
2. 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.
3. precipitation and concentration
   DNA is soluble in water and insoluble in alcohol
   - removes all the remaining cellular debris and unwanted material

Question 17

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 _________

Answer 17

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.)