MCQ practice

Question 1

If bacterial chromosome is digested by endonucleases in four sites giving rise to DNA fragments of which two are equal in length – How many bands would you see after agarose gel electrophoresis?
(A) 3
(B) 4
(C) 5
(D) Only one fragment
(E) None of the above

Answer 1

3- Because two of them are at the same length

Question 2

Which of the following statements is NOT true about agarose gel electrophoresis?

(A) Electrophoresis in agarose is a common way to separate DNA molecules according to size.

(B) Ethidium bromide is used to detect DNA.

(C) DNA migrates towards the cathode.

(D) Small DNA fragments migrate faster than larger ones.

(E) None of the above

Answer 2

C) DNA migrates towards the cathode

-In electrophoresis the DNA or the sample will always move towards the Anode which is the positive side (Goes from negative to positive)

Question 3

In PCR, if the oligonucleotides used were slightly shorter and more variable than the intended primers sequences?

A) PCR would not commence.
(B) PCR would stop after the first cycle.
(C) PCR would commence but a single short PCR product will be generated.
(D) A mixture of non-specific PCR products will be released.
(E) None of the above.

Answer 3

D) A mixture of non-specific PCR products will be released- Because it is not long enough

Question 4

Coomassie blue is used to stain …………………. in …………………….
(A) Gram positive bacteria in Gram staining.
(B) DNA fragments in SDS-PAGE.
(C) Proteins in agarose gel electrophoresis.
(D) DNA fragments in agarose gel electrophoresis.
(E) Proteins in sodium dodecyl sulphate–polyacrylamide gel electrophoresis

Answer 4

(E) Proteins in sodium dodecyl sulphate–polyacrylamide gel electrophoresis - That’s what Coomaasie brilliant blue staining is used for.

Question 5

A 53-year-old man has been feeling unwell and suffering general aches and pains, loss of appetite,diarrhoea and yellowish skin and eyes. Serum sample is collected for detection and quantificationof the DNA of hepatitis B virus (HBV) and the RNA of hepatitis C virus (HCV). Which technique you will use for detection and quantification of HBV and HCV?

(A) RT qPCR and RTPCR respectively.
(B) RT qPCR for both viruses.
(C) RTPCR and RT qPCR respectively.
(D) Reverse transcription polymerase chain reaction for both viruses.
(E) None of the above

Answer 5

(C) RTPCR and RT qPCR respectively.- (RT)-PCR assay is used for the detection, identification and quantification of hepatitis B virus (HBV), hepatitis C virus (HCV) and (HIV-1) in plasma or serum

Question 6

You are carrying out western blot for detection of hemagglutinin and neuraminidaseproteins of influenza A virus. The most commonly used gel in western blotting is:
(A) Agarose.
(B) Polyacrylamide.
(C) Both (A) and (B) are correct.
(D) Semisolid gel.(E) None of the above

Answer 6

(B) Polyacrylamide that is what is used for the SDS-PAGE

Question 7

In Gram staining, ……………. is used to fix the primary stain to bacterial cell wall while……………. is used as a secondary stain which stains Gram ……………… bacteria……………..
(A) Gram’s iodine, carbol fuchusin, positive, purple
(B) Ethanol, carbol fuchsin, negative, red
(C) Ethanol, safranin, negative, red
(D) Gram’s iodine, safranin, negative, red
(E) None of the above is correct

Answer 7

(D) Gram’s iodine, safranin, negative, red

Question 8

In agarose gel electrophoresis, for effective separation of …………… you will use 2% (w/v) of agarose in the gel while you use 0.8% (w/v) of agarose in the gel for the effective separation of……………
(A) Bacterial chromosome, specific bacterial gene.(B) Bacterial genome, specific bacterial gene.
(C) Specific bacterial gene, bacterial genome.
(D) Bacterial plasmid, specific bacterial gene.
(E) Larger size DNA fragments, smaller size DNA fragment

Answer 8

(C) Specific bacterial gene, bacterial genome.

Question 9

Which of these statements is FALSE about western blotting?

(A) Western blotting is more sensitive than Coomassie staining
(B) All of the above are true about western blotting
(C) Western blotting does not require a Coomassie staining step.
(D) Western blotting always requires an antibody.
(E) In western blotting the protein of interest acts as an antigen

Answer 9

(B) All of the above are true about western blotting

Question 10

In agarose gel electrophoresis, DNA will migrate towards …..?

(A) Negative electrode or cathode.
(B) Positive electrode or cathode.
(C) None of the above.
(D) Positive electrode or anode.
(E) Negative electrode or anode.

Answer 10

(D) Positive electrode or anode.

Question 11

The purpose of using bromophenol blue in the sample buffer in SDS-PAGE is to…..?

(A) Adjust the pH of the sample
(B) lonze the sample.
(C) Use it as a standard control
(D) Both C and Dare correct
(E) Monitor the electrophoretic run.

Answer 11

(E) Monitor the electrophoretic run.

Question 12

In SDS-PAGE, sodium dodecyl sulphate is used as ….?

(A) A cationic exchanger.
(B None of the above.
(C) A cationic detergent.
D) An anionic detergent.
(E) An anionic exchanger.

Answer 12

D) An anionic detergent. -Its positive

Question 13

Which of the following is TRUE for the SDS-PAGE?

(A) It cannot be used to separate proteins bound by cysteine bonds.
B) The main ingredient in the gel is agarose.
(C) It cannot be used to separate proteins that have an initial positive charge.
(D) It requires a protein-denaturing gel and buffer system.
(E) The samples can be visualised with ethidium bromide.

Answer 13

(D) It requires a protein-denaturing gel and buffer system.

Question 14

Gram staining distinguishes bacteria into Gram positive and Gram negative, based on their ………………
And…… bacteria retain crystal violet after the use of solvent?

(A) Cell wall, Gram positive.
B) Peptidoglycan, Gram negative.
(C Cell wall, acid fast.
D) LPS, Gram negative.
(E) Cell wall, Gram variable

Answer 14

(A) Cell wall, Gram positive.

Question 15

……. iS used for separation of proteins while ……….. is used for nucleic acid separation?

(A) Polyacrylamide, agarose.
(B) Agar, polyacrylamite.
C) None of the above.
(D) Agarose, polyacrylamide.
(E) Polyacrylamide, agar.

Answer 15

(A) Polyacrylamide, agarose.

Question 16

Which of the following medium is used for the culture and isolation of influenza virus?

(A) Nutrient agar.
(B Chromogenic agar.
(C) Sabouraud dextrose agar.
(D) None of the above is correct.
(E)MacConkey agar.

Answer 16

(D None of the above is correct. -Its golden standard its cultured and isolated in chicken eggs

Question 17

You carry out ELISA for detection of immunoglobulins M of hepatitis C virus, please arrange the steps about ELISA in chronological
order.

1- Incubate with the antibody-enzyme complex.
2- Transfer the antigen to a membrane, block unoccupied sites with nonspecific
3- incubate with the substrate.
4- Incubate with patients serum sample

(A) 2, 4, 3, 1.
(B) 2, 1, 3, 4.
(C) 2,4, 1, 3.
(D) 4, 2, 1, 3.
(E) 4, 1, 2, 3.

Answer 17

C) 2,4,1,3.- Transfer always happens first and the substrate always comes last

Question 18

In polymerase chain reaction, annealing involves
……. while denaturation involves …………….

(A) None of the above.
(B Heating between 90-98 °C, heating at 72 °C.
(C) Heating between 50-68 °C, heating between 90-98 °C.
D) Heating at 58-68 °C, heating at 72 °C.
(E) Heating at 72 °C, heating between 90-98 °C.

Answer 18

(C) Heating between 50-68 °C, heating between 90-98 °C. always remember 72 is extension the first two are ending with 5 at least within the range of numbers

Question 19

You extracted the genome of a bacterial strain of size 5 Mb which harbours 6 plasmids of sizes range from 10kb to 50k including two of the plasmids are of size 10kb.
When you carry out agarose gel electrophoresis of extracted plasmids, how many bands will appear on the gel image?

(A) 6
(B) 50
(C) 4
(D) 10
(E)5

Answer 19

(E) 5 if two are on the same one you count it as one

Question 20

Which of the follwing is FALSE about quantitative polymerase chain reaction?

(A) A negative result produces a negative Ct value.
(B) It cannot detect ribonucleic acid.
(C) The level of fluorescence depends on the amplification of target sequence.
(D) A positive result produces a positive Ct value.
(E) The dNTs are incorporated into the growing DNA strand during the extension step.

Answer 20

(B) It cannot detect ribonucleic acid.

Question 21

Which of the following is TRUE about real time PCR?

(A)Gel electrophoresis is required
(B) All of the above are the case.
(C) A thermal cycler is required.
(D) It cannot study gene expression.
(E) It cannot be used to quantify the DNA or RNA present in a sample.

Answer 21

(C) A thermal cycler is required.

Question 22

Which of the following is FALSE about enzyme linked immunosorbent assay?

(A) They can quantify the amounts of antigens in a sample.
(B) They can be easily automated.
(C) They can detect specific antibodies in a sample.
(D) They do not need radioactive substances.
(E) They do not require incubation steps.

Answer 22

(E) They do not require incubation steps.- Incubation is needed to allow for the binding kinetics to reach equilibrium

Question 23

In Gram staining, Candida species appear as …

(A) Purple cocci.
(B) Purple budding yeast cells.
(C) None of the above, Candida is a type of fungus and it does not stain with Gram staining.
(D) Pink budding yeast cells.
(E) Purple bacilli.

Answer 23

(B) Purple budding yeast cells.- Little purple bacteria clustered together

Question 24

The specificity of polymerase chain reaction is mostly determined by …………………….

(A) None of the above.
(B) Oligonucleotide sequence.
(C) Control samples.
(D) Taq polymerase.
(E) daNTPs.

Answer 24

(B) Oligonucleotide sequence.- , the specificity of PCR is controlled by the length of the oligonucleotide and the temperature of annealing

Question 25

Detection of specific immunoglobulins G antibodies of Mycobacterium tuberculosis in human’s serum by ELISA can NOT mean:

(A) The patient has a recent infection of TB.
(B) All of these are possible.
(C) The patient has had TB at some point in the past.
(D) None of the above.
(E) The patient has been vaccinated against TB.

Answer 25

(A) The patient has a recent infection of TB.