Ch 12- Forensic Serology Blood types and their antigens and antibodies. Agglutination. Whole blood typing. Characterizing a stain as blood. Significance of the precipitin test in serology. Absorption-elution techniques. Contribution of polymorphic enzymes and proteins to blood’s individualization.

Chromosomes and genes. Significance of Punnet square. Lab tests for seminal stauns. Preservation of stains for lab examination. Collection of physical evidence in rape investigation. ologytoxicology/intro.htm

DNA: abbreviation for deoxyribonucleic acid- the molecules carrying the body’s genetic information. DNA is double-stranded in the shape of a double helix Plasma: the fluid portion of unclotted blood Serum: the liquid that separates from the blood when a clot is formed Antigen: a substance, usually a protein that stimulates the body to produce antibodies against it

Antibody: a protein that destroys or inactivates a specific antigen. Antibodies are found in the blood serum Antiserum: blood serum in which there are specific antibodies Agglutination: the clumping together of red blood cells by the action of an antibody Serology: the study of antigen-antibody reactions Hemoglobin: a red blood cell protein responsible for transporting oxygen in the bloodstream and the red coloring of blood

Precipitin: an antibody that reacts with its corresponding antigen to form a precipitate Secretor: an individual who secretes his or her blood-type antigen(s) in body fluids. Approximately 80 percent of the population are secretors Enzyme: a type of protein that acts as a catalyst for certain specific reactions Polymorphism: the existence of more than one form of genetic trait

Iso-enzymes: multiple molecular forms of an enzyme, each having the same or very similar enzyme activities Gene: a unit of inheritance consisting of a DNA segment located on a chromosome Chromosome: a rodlike structure in the cell nucleus, along witch the genes are located. It is composed of DNA surrounded by other material, mainly proteins Egg: the female reproductive cell Sperm: the male reproductive cell

Zygote: the cell arising from the union of an egg and a sperm cell X-chromosome: the female sex chromosome Y-chromosome: the male sex chromosome Locus: the physical location of a gene on a chromosome Allele: any of several alternative forms of a gene located at the same point on a particular pair of chromosomes. For example, the genes determining the blood types A and B are alleles

Homozygous: having two identical allelic genes on two corresponding positions of a pair of chromosomes Heterozygous: having two different allelic genes on two corresponding positions of a pair of chromosomes Genotype: the particular combination of genes present in the cells of an individual Phenotype: the physical manifestation of a genetic trait such as shape, color, and blood type

Acid phosphatase: an enzyme found in high concentration in semen Oligospermia: a condition describing an abnormally low sperm count Aspermia: the absence of sperm; sterility in males

Ch 12 - Body Fluids Forensic Serology

Blood A complex mixture of cells, enzymes, proteins & inorganic substances Fluid portion of blood is called the plasma (55% of blood content) –primarily water –red cells (erythrocytes) –white cells (leukocytes) –platelets

What is Serology? A term which describes laboratory tests which employ a specific antigen and serum antibody reactions

Erythrocytes Transport oxygen from the lungs to the body tissues Transport carbon dioxide from the tissues to the lungs Red cells possess chemical structures on their surfaces called antigens or agglutinogens –impart blood type characteristics

Blood Type Three types (alleles) of blood type gene –A, B, O Each individual inherits one blood type gene from their mother & one from their father –6 possible combinations (genotypes) AA, BB, OO, AB, AO, and BO Genotype determines blood type

Antibodies or Agglutinins Proteins that are present in the serum responsible for ensuring that the only blood cells that can survive in a person are cells of the correct blood type

Antibodies produced by the A alleles remove any red blood cells containingB antigens by clumping them together Antibodies produced by the B alleles remove any red blood cells possessing A antigens

Type O Blood Possessed by people whose genotype is OO –both parents passed on the O gene –have no antigens these cells can be introduced into a person with Type A or Type B because these cells are not attacked by the antibodies these people possess –have both a & b antibodies can only have other O type cells mixed with this blood

Type A Possessed by people with genotype –AA –AO A is dominant to O Possesses antibody b –will destroy any Type B red cells –compatible with A or O red cells

Type B Possessed by people with genotype –BB –BO B is dominant to O Possesses antibody a –will destroy any Type A red cells –compatible with B or O red cells

Type AB Possessed by people with genotype –AB A & B are co-dominant Possesses no antibody –can have A, B, AB, or O cells added –Can’t be added to any other blood type without being destroyed by an antibody

Blood Typing Blood typing is done by reacting whole blood with antibody A and antibody B

Blood Typing

Relative Frequency of Blood Types in Human Populations