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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
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.