Forensic Biology Exam 1

What are the 5 steps in analyzing a crime scene?

1) Secure the scene

2) Record the scene

3) Search the scene

4) Collect evidence

5) Get reference samples

What is the first step for the first officer to the scene

Giving medical attention to any victims

What angle should close-up photos be taken at?

90 degrees

T/F: A final sketch includes everything that a rough sketch does.

True

T/F: Note taking should be constant during investigation of a crime scene.

True

What items should an evidence packager wear to avoid contamination?

Face mask, lab coat, and gloves

What is the definition of the Chain of Custody?

A list of all persons who came into possession of an item of evidence.

Where should initials be written on packaged evidence?

Over the seal

What is a reference sample?

Physical evidence whose origin is known (such as hair from a suspect)

What are the layers from top to bottom in separated blood?

Plasma, buffy coat, erythrocytes

What is the coagulation time for 1 mL of blood?

5-15 minutes

What portion of blood actually contains DNA?

White blood cells

Platelets and white blood cells are located in which layer of blood?

The buffy coat

What layer of blood is 90% water?

Plasma

What is the formula for angle of impact calculations?

sin(angle) = width / length

What angle stains will have a very elongated shape?

<< 90 degrees

What angle stains will have an almost perfectly circular shape?

~90 degrees

What is the difference between area of origin and area of convergence?

3-dimensional (includes height) vs. 2-dimensional

What is the formula for height of the area of origin?

tan(angle) = height / distance

What is a swipe pattern?

A blood-bearing surface transfers blood onto a clean surface

What is a wipe pattern?

A clean object moves through a surface with pre-existing blood stains

What kind of spatter is in the same direction as the projectile?

Forward spatter

What kind of spatter might come from the entrance wound of a gunshot?

Back spatter

What scientist discovered ABO blood groups?

Karl Landsteiner

What scientist discovered the antibody tests for ABO blood groups?

Leone Lattes

Who is the father of criminal profiling?

Hans Gross

Who made the theory regarding trace evidence?

Edmond Locard

What type of DNA polymorphisms are currently used in identifying people from their DNA?

STRs

What was the first type of DNA polymorphisms used in identifying people from their DNA?

VNTRs

T/F: Nucleic acids can be found in bodily fluids.

True

What is the role of the nucleolus?

It is the site of DNA transcription and where ribosomes are made

What type of cells are human sex cells / gametes?

Haploid (1N)

What type of cells are human somatic cells?

Diploid (2N)

How many total chromosomes are in each human somatic cell?

46

What is euchromatin?

Loosely packaged and expressible DNA

What is heterochromatin?

Tightly packaged and repressed DNA

What are the letters for the short and long arm of a chromosome?

Short = p, long = q

What are the three layers of the skin (external to internal)?

Epidermis, dermis, and hypodermis

What does touch DNA contain?

Small fragments of DNA from the skin shedding

What is the double swab technique used for?

Collection of touch DNA

T/F: A wet swab is used first for touch DNA.

True

When does cell death occur in hair cells?

When the hair approaches the dermis

What are the three phases of hair growth in order?

Anagen, catagen, and telogen

What hair growth phase is the best for gathering DNA?

Anagen

What DNA can be gathered from the shaft and root of hair?

Mitochondrial DNA

How many sets of DNA do mitochondria have?

1

How many pairs of nuclear DNA does a human somatic cell have?

23

Which cells are most abundant in bone?

Osteoblasts

What cells provide the most DNA in bone in general?

Osteoblasts

What bone cells have the most DNA and nuclei per cell?

Osteoclasts

What portion of blood contains DNA?

The buffy coat

What specific cells in the buffy coat contain DNA?

Leukocytes (white blood cells)

What type of reaction is the Kastle Meyer test?

Oxidation-reduction → results in a color change

What type of reaction is a chemiluminescent assay?

Oxidation-reduction → light is emitted as a product of oxidation

What type of reaction is a fluorescent assay?

Oxidation-reduction → oxidized product fluoresces under UV light

What can cause false positive and false negatives for blood tests?

False positives: Bleach, household cleaners, metal salts

False negatives: Plant peroxidases

What is the difference between an immunogen and an antigen?

Immunogen: causes an immune response

Antigen: any foreign substance, does not necessarily cause a reaction

What is an epitope?

The portion of an immunogen recognized by the antibody

What is agglutination?

The grouping of antibody-antigen complexes

What are haptens?

Antigens that do not elicit an immune response

What is the function of polyclonal antibodies?

They can bind to multiple different epitopes on a multivalent immunogen

What is the function of monoclonal antibodies?

They can only bind to one specific immunogen epitope

T/F: Immunoglobulins are proteins.

True

What is an immunoglobulin (Ig)?

A foreign antibody produced by plasma cells

What is an antiglobulin?

An antibody produced in response to an immunoglobulin

What is the difference between affinity and avidity?

Affinity: The binding of an antibody to a single epitope on an antigen

Avidity: The overall strength of the binding of an antibody and an antigen (combined strength of all binding sites)

What are the steps of a precipitation reaction?

1) Antigen-antibody form cross linked complexes

2) Complexes become insoluble and form a precipitate

What are precipitins?

Antibodies that produce precipitation

What are the steps of an agglutination reaction?

1) Initial binding of antibodies to antigens

2) Cross-links cause them to aggregate and form a lattice

What is the difference between agglutination and precipitation?

Agglutination: Involves an insoluble antigen

Precipitation: Involves a soluble antigen (can go back to being in solution)