Forensic Serology Questions and Answers

Q: If one of the parents is of O blood group, the blood group of the child cannot be :

The child cannot be AB.A parent of blood group O has genotype OO and can pass on only an O allele. For the child to be AB, it would need an A allele from one parent and a B allele from the other, which is impossible if one parent can give only O. This is the basis of the exclusion in disputed paternity cases.The child can be O (O from each parent), A (A from the other parent, giving AO) or B (B from the other parent, giving BO), so those three groups are all possible.

Q: DNA profiling cannot be carried out from :

DNA profiling cannot be done from erythrocytes.Mature human red blood cells lose their nucleus as they develop, so they contain no nuclear DNA. DNA profiles from blood come from the white blood cells (leucocytes), which are nucleated.Buccal smears contain nucleated epithelial cells from the inside of the cheek and are the standard reference sample. Semen contains spermatozoa, rich in nuclear DNA, and hair roots pulled out with the follicle carry nucleated cells. A cut hair shaft without its root has little nuclear DNA, but the option specifies the root tissue.

Q: Which of the following organs secrets zinc in large amounts in man ?

Zinc is secreted in large amounts by the prostate gland.Prostatic fluid is unusually rich in zinc, along with citric acid and acid phosphatase. Because of this, a high zinc content (shown for example by a zinc test) helps identify a stain as seminal fluid, and seminal zinc is used as a marker of prostate function.The seminal vesicles secrete fructose, the energy source of spermatozoa, and most of the volume of semen. The epididymis stores and matures sperm, and the vas deferens carries them; neither is a major source of zinc.

Q: Urea nitrate crystal test is used to identify :

The urea nitrate crystal test identifies urine.Urine contains urea in high concentration. When an extract of a suspected urine stain is treated with concentrated nitric acid, urea nitrate forms and crystallises as characteristic flat, rhombic or hexagonal plates that can be seen under the microscope. The test is a presumptive one, and urine is also recognised by its odour and by creatinine tests.Semen is identified by acid phosphatase, sperm and prostate-specific antigen, saliva by amylase, and sweat has no simple specific test. None is identified by urea nitrate crystals.

Q: Which of the following tests is best suited for species determination from semen stains ?

The best test is cross over electrophoresis.Species origin is decided by an antigen-antibody reaction with species-specific antisera. In crossover electrophoresis (counter-immunoelectrophoresis), the extract of the stain and the antiserum are placed in wells in a gel and an electric current drives them towards each other, so a precipitin line forms quickly where they meet. Driving the reactants together makes it much more sensitive and faster than the simple precipitin test, which suits the small amounts of protein in a dried semen stain.The ring precipitin test works on the same reaction, but it is less sensitive. Gel electrophoresis alone separates proteins without identifying the species, and the inhibition test is used for blood grouping.

Q: Fibrinogen and LDH are used for the identification of :

Fibrinogen and LDH are used to identify menstrual blood.Menstrual blood has two distinctive features. It has very little fibrinogen and does not clot, because it has already undergone fibrinolysis in the uterus. It also has a characteristic lactate dehydrogenase (LDH) isoenzyme pattern, with a raised LDH-4 and LDH-5 fraction compared with circulating blood. Together these distinguish menstrual blood from blood from a wound, which can matter in sexual offence cases.Saliva is identified by amylase, and semen by acid phosphatase, sperm and p30 (PSA), so neither depends on fibrinogen and LDH.

Q: Blood group specific antigens are found on the surface of :

Blood group specific antigens are found on the surface of erythrocytes.The ABO and Rh blood groups are defined by antigens on the red cell membrane. In the ABO system they are carbohydrate chains of glycoproteins and glycolipids: A antigen on group A cells, B on group B cells, both on AB, and neither on O. Matching these red-cell antigens is the basis of blood transfusion and of blood grouping of stains in forensic serology.Leucocytes carry the HLA antigens used in tissue typing, which are a different system. Platelets (thrombocytes) and neutrophils (a type of leucocyte) carry their own antigens, but blood groups in the usual sense are red-cell antigens.

Q: Which of the following is involved in the immune system of human body ?

The cells involved in the immune system are the leucocytes.White blood cells defend the body. Neutrophils and monocytes engulf microorganisms, lymphocytes provide specific immunity (B cells make antibodies and T cells kill infected cells and coordinate the response), and eosinophils and basophils take part in allergic and parasitic responses.Erythrocytes carry oxygen, and thrombocytes (platelets) are concerned with clotting. Serum carries antibodies made by B lymphocytes, but it is the fluid left after clotting, not the immune cells themselves, which is why the leucocytes are the answer.

Q: Species of origin of a blood stain can be detected with the help of :

Species of origin is determined by the precipitin test.The precipitin test uses antisera raised against the serum proteins of a species, for example anti-human serum. When an extract of the stain meets the matching antiserum, an antigen-antibody precipitate forms (in a ring test, gel diffusion or crossover electrophoresis), showing that the blood is human or from the species tested.The orthotoluidine test is a presumptive test for blood that does not tell the species. The absorption-inhibition and absorption-elution tests are methods for determining ABO blood group in stains.

Q: Mitochondrial DNA is inherited from :

Mitochondrial DNA is inherited from the mother.Mitochondria are passed on through the egg's cytoplasm. The few paternal mitochondria in the sperm are destroyed after fertilisation, so a person's mtDNA is the same as their mother's, their siblings' and all their maternal relatives'. This makes it useful in forensic identification when nuclear DNA is degraded, as in old bones, teeth and hair shafts.It is not inherited from the father or from both parents; that is nuclear DNA. Father-to-son inheritance is the pattern of the Y chromosome.

If one of the parents is of O blood group, the blood group of the child cannot be :

A.AB
B.A
C.O
D.B

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

The child cannot be AB.

A parent of blood group O has genotype OO and can pass on only an O allele. For the child to be AB, it would need an A allele from one parent and a B allele from the other, which is impossible if one parent can give only O. This is the basis of the exclusion in disputed paternity cases.

The child can be O (O from each parent), A (A from the other parent, giving AO) or B (B from the other parent, giving BO), so those three groups are all possible.

Discuss in Forum

DNA profiling cannot be carried out from :

A.Erythrocytes
B.Buccal smear samples
C.Semen samples
D.Hair root tissue

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

DNA profiling cannot be done from erythrocytes.

Mature human red blood cells lose their nucleus as they develop, so they contain no nuclear DNA. DNA profiles from blood come from the white blood cells (leucocytes), which are nucleated.

Buccal smears contain nucleated epithelial cells from the inside of the cheek and are the standard reference sample. Semen contains spermatozoa, rich in nuclear DNA, and hair roots pulled out with the follicle carry nucleated cells. A cut hair shaft without its root has little nuclear DNA, but the option specifies the root tissue.

Discuss in Forum

Which of the following organs secrets zinc in large amounts in man ?

A.Seminal vesicles
B.Prostate gland
C.Epididymis
D.Vas deferens

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

Zinc is secreted in large amounts by the prostate gland.

Prostatic fluid is unusually rich in zinc, along with citric acid and acid phosphatase. Because of this, a high zinc content (shown for example by a zinc test) helps identify a stain as seminal fluid, and seminal zinc is used as a marker of prostate function.

The seminal vesicles secrete fructose, the energy source of spermatozoa, and most of the volume of semen. The epididymis stores and matures sperm, and the vas deferens carries them; neither is a major source of zinc.

Discuss in Forum

Urea nitrate crystal test is used to identify :

A.Semen
B.Urine
C.Sweat
D.Saliva

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The urea nitrate crystal test identifies urine.

Urine contains urea in high concentration. When an extract of a suspected urine stain is treated with concentrated nitric acid, urea nitrate forms and crystallises as characteristic flat, rhombic or hexagonal plates that can be seen under the microscope. The test is a presumptive one, and urine is also recognised by its odour and by creatinine tests.

Semen is identified by acid phosphatase, sperm and prostate-specific antigen, saliva by amylase, and sweat has no simple specific test. None is identified by urea nitrate crystals.

Discuss in Forum

Which of the following tests is best suited for species determination from semen stains ?

A.Gel electrophoresis
B.Precipitin test
C.Cross over electrophoresis
D.Inhibition test

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

The best test is cross over electrophoresis.

Species origin is decided by an antigen-antibody reaction with species-specific antisera. In crossover electrophoresis (counter-immunoelectrophoresis), the extract of the stain and the antiserum are placed in wells in a gel and an electric current drives them towards each other, so a precipitin line forms quickly where they meet. Driving the reactants together makes it much more sensitive and faster than the simple precipitin test, which suits the small amounts of protein in a dried semen stain.

The ring precipitin test works on the same reaction, but it is less sensitive. Gel electrophoresis alone separates proteins without identifying the species, and the inhibition test is used for blood grouping.

Discuss in Forum

Fibrinogen and LDH are used for the identification of :

A.Saliva
B.Menstrual blood
C.Semen
D.Saliva, semen and menstrual blood

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

Fibrinogen and LDH are used to identify menstrual blood.

Menstrual blood has two distinctive features. It has very little fibrinogen and does not clot, because it has already undergone fibrinolysis in the uterus. It also has a characteristic lactate dehydrogenase (LDH) isoenzyme pattern, with a raised LDH-4 and LDH-5 fraction compared with circulating blood. Together these distinguish menstrual blood from blood from a wound, which can matter in sexual offence cases.

Saliva is identified by amylase, and semen by acid phosphatase, sperm and p30 (PSA), so neither depends on fibrinogen and LDH.

Discuss in Forum

Blood group specific antigens are found on the surface of :

A.Erythrocytes
B.Leucocytes
C.Thrombocytes
D.Neutrophils

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

Blood group specific antigens are found on the surface of erythrocytes.

The ABO and Rh blood groups are defined by antigens on the red cell membrane. In the ABO system they are carbohydrate chains of glycoproteins and glycolipids: A antigen on group A cells, B on group B cells, both on AB, and neither on O. Matching these red-cell antigens is the basis of blood transfusion and of blood grouping of stains in forensic serology.

Leucocytes carry the HLA antigens used in tissue typing, which are a different system. Platelets (thrombocytes) and neutrophils (a type of leucocyte) carry their own antigens, but blood groups in the usual sense are red-cell antigens.

Discuss in Forum

Which of the following is involved in the immune system of human body ?

A.Erythrocytes
B.Leucocytes
C.Serum
D.Thrombocytes

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The cells involved in the immune system are the leucocytes.

White blood cells defend the body. Neutrophils and monocytes engulf microorganisms, lymphocytes provide specific immunity (B cells make antibodies and T cells kill infected cells and coordinate the response), and eosinophils and basophils take part in allergic and parasitic responses.

Erythrocytes carry oxygen, and thrombocytes (platelets) are concerned with clotting. Serum carries antibodies made by B lymphocytes, but it is the fluid left after clotting, not the immune cells themselves, which is why the leucocytes are the answer.

Discuss in Forum

Species of origin of a blood stain can be detected with the help of :

A.Orthotoluidine Test
B.Precipitin Test
C.Inhibition Test
D.Elution Test

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

Species of origin is determined by the precipitin test.

The precipitin test uses antisera raised against the serum proteins of a species, for example anti-human serum. When an extract of the stain meets the matching antiserum, an antigen-antibody precipitate forms (in a ring test, gel diffusion or crossover electrophoresis), showing that the blood is human or from the species tested.

The orthotoluidine test is a presumptive test for blood that does not tell the species. The absorption-inhibition and absorption-elution tests are methods for determining ABO blood group in stains.

Discuss in Forum

10.

Mitochondrial DNA is inherited from :

A.Father
B.Both Father and Mother
C.Mother
D.Father and Grandfather

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

Mitochondrial DNA is inherited from the mother.

Mitochondria are passed on through the egg's cytoplasm. The few paternal mitochondria in the sperm are destroyed after fertilisation, so a person's mtDNA is the same as their mother's, their siblings' and all their maternal relatives'. This makes it useful in forensic identification when nuclear DNA is degraded, as in old bones, teeth and hair shafts.

It is not inherited from the father or from both parents; that is nuclear DNA. Father-to-son inheritance is the pattern of the Y chromosome.

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