Forensic Serology and Biology

Forensic Serology and Biology

Here is the List of Questions with Answers along with explanation

Que 1. What is the range of pH of Human Blood?

 a) 6 – 7

 b) 7 – 8

 c) 7.35 – 7.45

 d) 7.15 – 7.25

Answer - (d) slightly alkaline

Explanation: Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma .The pH scale, ranges from 0 (strongly acidic) to 14 (strongly basic or alkaline). A pH of 7.0, in the middle of this scale, is neutral. Blood is normally slightly basic, with a normal pH range of about 7.35 to 7.45. Usually the body maintains the pH of blood close to 7.40.

Que 2. Who discovered ABO blood grouping?

a) Edward Jenner

b) Karl Landsteiner

c) Alexander Wiener

d) Jan Jansky

Answer - (b) Karl Landsteiner

Explanation: The ABO blood types were discovered by Karl Landsteiner in 1901; he received the Nobel Prize in Physiology or Medicine in 1930 for this discovery. ABO blood types are also present in other primates such as apes and Old World monkeys. The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes.

Que 3. What is immunogen?

 a) Antigen

 b) Antibody

 c) Antigen which elicit antibody formation

 d) RBC

Answer -  (c) Antigen which elicit antibody formation

Explanation: An immunogen is a specific type of antigen that is able to elicit an immune response. Antibody development is dependent on a humoral immune response mediated by immune cells recognizing a molecule as being foreign. Injecting an immunogen in the presence of an adjuvant pushes the immune system of the host to elicit a specific immune response, generating antibodies against the target.

Que  4. Immunoglobulin’s are categorized into ……………. classes.

 a) Four

 b) Five

 c) Six

 d) Two

Answer - (b) Five

Explanation: The five primary classes of immunoglobulins are IgG, IgM, IgA, IgD and IgE. These are distinguished by the type of heavy chain found in the molecule. IgG molecules have heavy chains known as gamma-chains; IgMs have mu-chains; IgAs have alpha-chains; IgEs have epsilon-chains; and IgDs have delta-chains. Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells).

Que 5. What is Benzidine Test used for?

 a) Blood presumptive test

 b) Blood Origin

 c) Blood grouping

 d) Both A and B

Answer - (a) Blood presumptive test

Explanation: Benzidine test is one of  the presumtive test for blood. The benzidine-hydrogen dioxide test for minute quantities of blood, introduced by Adler. An enzyme in blood causes the oxidation of benzidine to a distinctively blue-coloured derivative. It is a sensitive test for the presence of blood (as in urine or feces) based on the production of a blue color upon contact with a solution of benzidine, hydrogen peroxide, and glacial acetic acid.

Que 6. The sensitivity of Benzidine Test on blood is………….

 a) 1:100

 b) 1:1000

c) 1:10000

d) 1:500000

Answer - (d) 1:500000 dilution

Explanation: The benzidine-hydrogen dioxide test for minute quantities of blood, introduced by Adler, is  a sensitive test for the presence of blood (as in urine or feces) based on the production of a blue color upon contact with a solution of benzidine, hydrogen peroxide, and glacial acetic acid. The sensitivity of benzidine reagent is so high that if there is 1:10 ratio ,that is 1 ml sample of blood and 9 ml of water then also the reagent will give positive test. Therefore, option (D) that is 1:500000 is the correct answer.

Que 7. Invisible stains of blood is detected by

a) Benzidine Test

 b) KM Test

 c) Luminol Test

d) Takayama Test

Answer - (c) Luminol Test

Explanation: At present, blood stains are detected using the chemical luminol, which is sprayed around the crime scene and reacts with the iron in any blood present to emit a blue glow that can be seen in the dark. However, luminol has certain disadvantages — it is potentially toxic, it has been reported to dilute blood solutions below the limits needed to detect DNA, it can smear blood spatter patterns that could otherwise yield insights on how a crime was committed, and it can provide false positive results.

Que 8. ……………….   can give False Positive Test in presence of contaminants, chemical oxidants, catalysts, plant peroxidases etc .

a) Luminol Test

b) Leucomalachite Green Test

c) Benzidine Test

d ) Orthotolidine Test

Answer - (c) Benzidine Test

Explanation: Benzidine-based tests (e.g., Hematest) have been virtually eliminated from use because of their excessive sensitivity, which results in a high frequency of false-positive reactions, as well as the carcinogenicity of the reagent.  A false positive test can occur in presence of contaminants, chemical oxidants, catalysts, plant peroxidases etc that is another substance reacting the same way, producing the expected result. 

Que 9. What is absorption spectra of hemoglobin and its derivatives for blood identification?

 a) 220 – 230nm

 b) 430 – 440nm

 c) 540 – 560nm

 d) 650 – 680nm

Answer -  (c)  540 – 560nm

Explanation: In the CO-oximeter absorbance measurements of a hemolyzed blood sample at multiple wavelengths across the range that hemoglobin species absorb light (520-620 nm) are used by the installed software to calculate the concentration of each of the hemoglobin derivatives (HHb, O2Hb, MetHb and COHb).Therefore answer 540-560 nm is correct as it comes in between range 520 -560 nm. 

Que 10. Double Diffusion Technique is used for

a) Identification of blood

b) Identification of Semen

c) Identification of Origin of Blood

d) None of these.

Answer - (c) Identification of Origin of Blood

Explanation: Immuno-diffusion is a technique used for the detection or measurement of antibodies and antigens by their precipitation which involves diffusion through a substance such as agar or gel agarose. Simply, it denotes precipitation in gel that is used for the identification of origin of blood. In double immuno-diffusion, both the antibody and antigen are allowed to diffuse into the gel. After application of the reactants in their respective compartments, the antigen and the antibody diffuse toward each other in the common gel and a precipitate is formed at the place of equivalence.

Que 11. The plant whose seeds are used as agglutinating protein for blood grouping is

a) Lantana indica

b) Pisum sativum

c) Ulex europaeus

d) Ginkgo biloba

Answer -  (c) Ulex europaeus

Explanation: Ulex europaeus seeds contain two agglutinins an l-fucose-binding lectin (U. europaeus I, UEA I) and U. europaeus II (UEA II), which is most potently inhibited by N-acetylated chitodextrins and l-Fuc(α1–2)Gal(β1–4)GlcNAc.  Additional substances with specific blood group activity have been found in certain plants. Plant agglutinins are called lectins. Some useful reagents extracted from seeds are anti-H from Ulex europaeus (common gorse); anti-A1, from another member of the pulse family Fabaceae (Leguminosae), Dolichos biflorus; and anti-N from the South American plant Vicia graminea. 


Que 12. Seeds of Ulex europaeus contains

a) Lectins

b) Glucose

c) Cytokinin

d) Lipids

Answer - (a) Lectins

Explanation: Lectin extracted from seeds of Ulex europaeus binds to, is remarkably specific for, and is the standard method for identification of H-substance (absent in the hh antigen system) on human red blood cells. The vast majority of humans express H-substance, which is the basis for the ABO blood group system, but a few rare individuals ("Bombay phenotype") do not—and a chemical isolated from Ulex europaeus is used to identify these individuals. This lectin is also used as a marker for human vascular endothelial cells, and as a tool for their isolation for in-vitro culture.


Que 13. In which type of blood group agglutination does not take place by antigen A, antigen B, antigen H?

a) O blood group

b) Bombay blood group

c) AB blood group

d) None

Answer -  (b) Bombay blood group

Explanation: Individuals who are homozygous for null alleles at this locus (h/h) do not produce H antigen, and because the H antigen is an essential precursor to the ABO blood group antigens, they cannot produce A and B antigens. Therefore, their serum contains anti-A and anti-B, in addition to potent anti-H. This rare phenotype of H-deficient RBCs is called the "Bombay phenotype" (Oh) after the city in which it was first discovered. Individuals with the Bombay phenotype are healthy, but if they ever needed a blood transfusion, the antibodies in their serum would place them at a high risk of having an acute hemolytic transfusion reaction. This can be avoided by using only blood products from a donor who also has the Bombay phenotype (usually a relative).

Que 14. Christmas tree strain test is confirmatory test for

a) Blood

 b) Origin

 c) Grouping

 d) Spermatozoa

Answer -  (d) Spermatozoa

Explanation: The most reliable confirmation for the presence of semen is the positive visual identification of sperm cells (or spermatozoa) using the Christmas tree stain. Two main reagents are used consecutively to produce this distinctive stain: Picroindigocarmine stains the neck and tail portions of the sperm in green and blue, while Nuclear Fast Red (also known as Kernechtrot) gives the sperm heads a red color and the tips of the heads, an area known as acrosomal cap, a pink color.  Although this color pattern seems quite unique and may render sperm cells easily distinguishable under a microscope, sperm cells tend to deteriorate quickly after ejaculation. 

Que 15. For Semen analysis (especially in case of Vasectomized, Oligospermic and Aspermic males) test conducted is

a) Mixed agglutination

b) PSA test

c) Luminol test

d) Christmas tree strain

Answer - (b) PSA test

Explanation: If a male is aspermic or oligospermic, they either have no sperm or a low sperm count. Vasectomized males will not release sperm either. When sperm cells are not present, a second confirmatory test, the p30/PSA test, is performed. PSA(p30) is known as a prostate-specific antigen that is produced by the prostatic gland in males. The p30/PSA test is an immune chromatographic test that detects the presence of the antigen p30 in semen samples. This test functions similar to a pregnancy test, where if the antigen p30 is present a band will appear at the test site and a control band will appear to confirm if the test is working properly. If the confirmatory test is positive, then semen is present in the sample. 

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