HOSA Forensic Science: Serology and Biological Fluids Practice Questions & Answers

Antigens are substances (usually proteins or carbohydrates) on the surface of red blood cells that determine blood type. Antibodies are immune proteins found in the plasma/serum that react specifically with foreign antigens.

Agglutination with anti-A serum indicates the presence of A antigens on the red blood cells. Since it does not agglutinate with anti-B serum, B antigens are absent, meaning the blood is Type A.

Type O negative (O-) blood lacks A, B, and Rh(D) antigens on the surface of red blood cells, minimizing the chance of an adverse immune reaction, making it the universal donor.

The Rh blood group system is complex, but the 'positive' or 'negative' designation specifically refers to the presence or absence of the D antigen.

Agglutination is the clumping of particles. In blood typing, antibodies attach to multiple red blood cells simultaneously via their surface antigens, pulling them into visible clumps.

Mature red blood cells in mammals lack a nucleus and DNA. Leukocytes (white blood cells) contain nuclei and are the primary source of nuclear DNA in bloodstains.

A secretor is a person who secretes their blood type antigens into body fluids such as saliva, tears, and semen. About 80% of the human population are secretors.

A person with Type AB blood has both A and B antigens on their red blood cells. Therefore, their immune system will not produce either anti-A or anti-B antibodies; doing so would attack their own cells.

Agglutination with anti-B signifies the presence of the B antigen. Agglutination with anti-D signifies the presence of the Rh factor (positive). Thus, the type is B+.

Antibodies are typically Y-shaped proteins. The tips of the 'Y' contain variable regions that specifically bind to the target antigens.