Multiple choice question for engineering
Set 1
1. If expression of the coding sequence is to be carried in the vitro, then which of the statement holds true?
a) The extract in which the host DNA constructs are incubated is capable of translation only
b) The extract in which the host DNA constructs are incubated is capable of transcription only
c) The extract is made up of lysate of E. coli cells, containing RNA polymerase, ribosomes, tRNAs etc.
d) Non radiolabelled amino acids are used
Answer
Answer: c [Reason:] If expression of the coding sequence is to be carried in vitro, then the extract in which host DNA constructs are incubated is capable of both transcription and translation. The extract is made up of lysate of E. coli cells, containing RNA polymerase, ribosomes, tRNAs etc. Radiolabelled amino acids are used and thus detection becomes easier.
2. If translation and transcription are taking place together, the reaction is called as ______ and if they are carried out separately, it is called as _______
a) coupled, linked
b) linked, coupled
c) grouped, separate
d) grouped, individual
Answer
Answer: a [Reason:] If translation and transcription are carried out together, it is known as coupled reaction. If they are carried out separately then they are known as linked reactions.
3. If translation and transcription are carried out separately, then what is added to carry out translation?
a) DNA polymerase
b) RNA polymerase
c) Taq polymerase
d) Tfl polymerase
Answer
Answer: b [Reason:] The added RNA polymerase carries out the translation in a separate reaction by the use of lysate of wheat gram cells.
4. If the screening of the DNA constructs is carried out in pooled batches then it takes less time. Is the given statement true or false?
a) True
b) False
Answer
Answer: a [Reason:] If the screening of DNA constructs is carried out in pooled batches then less time is taken. Once the pooled batch is identified with recombinants then each member is screened.
5. Choose the incorrect statement for open reading frame.
a) It is helpful in deciding whether the clone is correct or not
b) It consists of an initiation codon
c) It consists of termination codon
d) The presence of introns doesn’t affects the open reading frame
Answer
Answer: d [Reason:] Open reading frame is very important in deciding whether the clone is correct or not. It consists of an initiation codon, followed by a stretch of DNA and termination codon. The presence of introns the open reading would be affected and makes detection difficult.
6. Introns are ________ in nature and the sequence is _______ than exons.
a) coding, less random
b) non-coding, less random
c) non-coding, more random
d) coding, more random
Answer
Answer: c [Reason:] Introns are non-coding in nature and thus the sequence is having a more random base composition than exons. Exons are coding sequences.
7. If the genome size is small, then sequencing of the entire genome is:
a) easy
b) difficult
c) independent of the size of genome
d) not possible
Answer
Answer: a [Reason:] If the genome size is small, then the sequencing of entire genome is carried out easily. Hence, direct sequencing is carried out if the genome size is small.
8. Choose the correct statement with respect to bacterial genome.
a) They are easy to sequence
b) They are difficult to sequence
c) Methods such as transcription and translation are satisfactory
d) Only transcription can be carried out
Answer
Answer: b [Reason:] Bacterial genome is of large size and thus it is difficult to carry out sequencing. Methods such as transcription and translation are unsatisfactory.
9. For identification of genes that are expressed under special conditions, _______ libraries are used.
a) cDNA
b) genomic
c) subtractive
d) shelf
Answer
Answer: c [Reason:] If genes are expressed under special conditions then specialized libraries should be used. These specialized libraries are subtractive. In this, driver and tracers are used.
10. In ______ organisms, firstly the gene is looked into model organisms.
a) eukaryotic
b) prokaryotic
c) both eukaryotic and prokaryotic
d) large sized
Answer
Answer: a [Reason:] In eukaryotic organisms, firstly the gene is looked into the model organism. In the model organism, the genome size is small. Eukaryotic organisms generally have a varying size of genome.
Set 2
1. If overexpression of proteins takes place, they become toxic at times. In such a case, _______ colonies are recovered after ______ with the recombinant plasmid.
a) few, translation
b) few, transformation
c) no, transformation
d) no, translation
Answer
Answer: c [Reason:] At times, overexpression of proteins takes place. It leads to toxicity. In such a case, no colonies are recovered after transformation with the recombinant plasmid. It is so because, no colonies survive because of overexpression of the protein.
2. Ribosome binding site in E.coli is composed of which sequence primarily?
a) -GAGG-
b) -CTCC-
c) -ATGG-
d) -CGTT-
Answer
Answer: a [Reason:] Ribosome binding site is responsible for initiating translation. It is composed of –GAGG- sequence primarily.
3. Translation starts at first _____ codon in the mRNA downstream from the ribosome binding site.
a) ACG
b) AUG
c) UAC
d) CAG
Answer
Answer: b [Reason:] Translation starts at first AUG codon in the mRNA downstream from the ribosome binding site. It is the start codon.
4. Expression of cloned sequences in E.coli requires a promoter, a ribosome binding site and an initiation codon. Is the given statement true or false?
a) True
b) False
Answer
Answer: a [Reason:] Expression of cloned sequences in E. coli requires a promoter, a ribosome binding site and an initiation codon. Initiation codon is the start codon AUG.
5. If an expression vector contains all three, viz. a controllable promoter, a ribosome binding site and an initiation codon, then a hybrid protein is produced. The _______ region of hybrid protein is encoded by vector and the rest is expressed by the sequence inserted.
a) N terminal
b) C terminal
c) both N & C terminal
d) middle
Answer
Answer: a [Reason:] If all three elements are present, then a hybrid protein is formed. The N terminal region of the hybrid protein is encoded by the vector and the rest is expressed by the sequence inserted.
6. Proteins synthesized by carrying out translation of the vector region and continuing it in the insert region is called as:
a) hybrid protein
b) fusion protein
c) combination protein
d) insert protein
Answer
Answer: b [Reason:] At times, translation of vector is carried out and is continued in the insert. Proteins produced by this method are known as fusion proteins.
7. It is also possible to generate a fusion protein in which ______ is encoded by the vector.
a) N terminal
b) C terminal
c) both N and C terminal
d) middle region
Answer
Answer: b [Reason:] Generally, N terminal is encoded by the vector. But at times it is also possible to generate a fusion protein by encoding C terminal.
8. Which of the following is present in E. coli rrnB operon for rRNA?
a) Initiation codon
b) Termination codon
c) Both initiation and termination codon
d) Both are absent
Answer
Answer: c [Reason:] Initiation codon is present in all expression vectors, but few are also having termination codons. It is necessary to stop high levels of transcription.
9. Termination codon is required for stopping high levels of transcription of other region such as _______ which might interfere with ____ of the vector.
a) origin, replication
b) end, replication
c) end, stability
d) origin, stability
Answer
Answer: d [Reason:] Termination codon is required for stopping high levels of transcription of other regions such as origin. Other regions might interfere with the stability of the vector.
10. In fusion proteins the reading frame in vector is out of phase with the insert. Is the given statement true or false?
a) True
b) False
Answer
Answer: b [Reason:] Fusion proteins are the proteins produced by carrying the translation in vector region and then continuing it in insert region. Hence, to carry out this, the reading frame should be in phase.
Set 3
1. A piece of DNA that is to be separated is crushed and soaked into the buffer. The majority of DNA diffuses, how can it be separated?
a) Filtration and centrifugation
b) Filtration or centrifugation
c) Allowing to sediment
d) By passing through silica column
Answer
Answer: b [Reason:] As the target DNA is crushed and soaked into the buffer, the majority of it diffuses into the gel. It can be separated via filtration or separation. It is simply termed as recovering the DNA from the gel by diffusion.
2. Another method of DNA recovery is termed as freeze-squeeze. The correct statement for it is?
a) The slice containing DNA is cut and frozen into liquid oxygen
b) Freezing doesn’t have any effect on the DNA structure
c) After freezing centrifugation is carried out through glass wool plug
d) The substance used for centrifugation allows the gel to pass through but the liquid is retained
Answer
Answer: c [Reason:] It is also a method for obtaining DNA from gels. The slice containing DNA is cut and frozen into liquid nitrogen. Freezing in liquid nitrogen leads to disruption of structure. As the centrifugation by glass wool plug is carried out after freezing out, the gel is retained by it. The liquid which is containing dissolved DNA will be allowed to pass through.
3. If further electrophoresis is used for recovery of DNA from gels, the method is termed as:
a) secondary electrophoresis
b) recovery electrophoresis
c) denaturing electrophoresis
d) electro-elution
Answer
Answer: d [Reason:] If electrophoresis is used further for recovery, the method is termed as electro-elution. There are different electro-elution methods which are used such as dialysis tube or membrane is used.
4. The DNA is sliced and is placed into the dialysis tube containing buffer. Further electrophoresis is performed. After it, the DNA moves out of the gel but is retained by buffer. The given statement is true or false?
a) True
b) False
Answer
Answer: a [Reason:] As further electrophoresis is carried out, the DNA moves out of the gel but is retained by the buffer. From the buffer it can be obtained via pipetting.
5. UV shadowing is used at times for visualising the DNA. Which of the statements is correct for it?
a) In this method, the DNA bands are visualized because they fluoresce under UV
b) The DNA bands won’t fluoresce but will absorb the UV light
c) It is not suitable for visualizing single stranded molecules
d) It is less preferred over use of ethidium bromide
Answer
Answer: b [Reason:] In this method, the DNA bands won’t fluoresce but will absorb the UV light. This leads to the formation of a non-fluorescent shadow on the screen. It is suitable for visualising single stranded species because the mode of action is not intercalating as in the case of use of ethidium bromide. It is preferred over it because ethidium bromide is often difficult to remove.
6. The greatest separation is obtained in which portion of the gel?
a) Lower portion where the anode is
b) Lower portion where the cathode is
c) The separation is uniform all over
d) It varies according to the quantity of the size of the molecules to be separated
Answer
Answer: a [Reason:] The greatest separation is obtained in the lower portion of the gel where the anode is. Thus the smaller molecules are having the greatest separation because they are the one which travel farther in the gel.
7. Which of the statements is correct for non uniform separation obtained other than the conventional one?
a) It can be obtained via applying strong field towards the cathode
b) It can be obtained via applying same field on both the sides
c) The separation is greater on the side of stronger field
d) Its is greater towards the weaker field
Answer
Answer: c [Reason:] Conventionally, separation is greater towards the lower portion i.e. where the anode is. In order to obtain greater separation towards the cathode, the stronger field is applied here. As the field is weaker on the anode side, the molecules retard as they move towards anode and are less separated.
8. How can gradient in the field strength be obtained?
a) It can be obtained via varying the amount of current, keeping the resistance constant
b) It can be obtained via varying the amount of resistance, keeping the current constant
c) Both can be varied, but resistance is having more effect
d) Buffer-gradient gels can be used with decreasing concentration of buffer at the bottom.
Answer
Answer: b [Reason:] The gradient field strength can be obtained via varying the resistance because the current flowing throughout the gel needs to remain constant. To vary the resistance, often buffer-gradient gels and wedge gels can be used. Wedge gels are thick and thus are having lower resistance at the bottom. Whereas buffer-gradient gels with increasing concentration at the bottom are used. As the concentration increases at the bottom, resistance decreases.
9. If the molecules to be separated are larger than the size for conventional electrophoresis, which type of gels can be used?
a) Wedge gels
b) Buffer-gradient gels
c) Pulse field gels
d) Varying the amount of agarose, will carry out the separation
Answer
Answer: c [Reason:] In the case, if the molecules to be separated are very large, say the chromosomes are to be separated. In this case, pulse-field gels are used. It is termed as pulse field gel electrophoresis (PFGE).
10. Which of the following statement is correct for the method of separation of large molecules?
a) The large DNA molecules can pass through the matrix in any direction, not necessarily in the direction parallel to the movement
b) The separation can be carried out if the fields are at right angles to each other
c) The time of pulse should be less than that of the reorientation time
d) Separation is not of the megabase level
Answer
Answer: b [Reason:] For the separation of large DNA molecules, the electric fields are often applied at right angles to each other. Usually, the large molecules pass through the matrix only in the direction of the movement. In rest directions, the movement is blocked by the gel matrix. The time of pulse is greater than that of the reorientation time. Thus, smaller molecules have greater time for movement. DNA of megabase size can also be separated.
Set 4
1. There are some advantages of expressing protein as a fusion protein. It may enhance stability, folding, ______ and ______ formation.
a) solubility, phosphodiester bond formation
b) insolubility, phosphodiester bond formation
c) solubility, disulphide bond formation
d) insolubility, disulphidebond formation
Answer
Answer: c [Reason:] Expressing a protein as a fusion protein is advantageous. It may enhance stability, folding, solubility and disulphide bond formation.
2. A short peptide region fused to a protein of interest is known as:
a) tag
b) oligonucleotide
c) fragment
d) dimer
Answer
Answer: a [Reason:] A short peptide region (generally, a few nucleotides long) is fused to a protein of interest and is known as tag.
3. Glutathione-S-Transferase (GST) enzyme is used for conjunction of Glutathione molecules and is having a protective function in many organisms. Is the given statement true or false?
a) True
b) False
Answer
Answer: a [Reason:] GST enzyme is used for conjunction of Glutathione molecules and is also having a protective function in many organisms. It is widely used as a basis for fusion proteins.
4. Maltose binding protein is the product of ______ gene in E.coli and located in ______
a) malE, nucleus
b) malD, nucleus
c) malE, periplasmic space
d) malD, periplasmic space
Answer
Answer: c [Reason:] Maltose binding protein is the product malE gene in E.coli and is located in the periplasmic space. It is responsible for uptake of maltose and other sugars.
5. Thioredexin protein contains two _______ residues.
a) cysteine
b) cystine
c) adenine
d) guanine
Answer
Answer: a [Reason:] This protein contains two cysteine residues and they are reversibly oxidized to cystine residues.
6. Often, protein to be expressed is fused with histidine and it is called as histidine tags. For their purification, matrix containing ______ is used.
a) calcium ions
b) nickel ions
c) iron ions
d) fluorine ions
Answer
Answer: b [Reason:] Histidine tags are use in place of naturally occurring protein at times for fusion proteins. For purification, matrix containing nickel ions is used and it based on affinity purification.
7. Pel B protein is produced in plants and helps in degradation of ______
a) vacuole
b) plasma membrane
c) cell wall
d) mitochondria
Answer
Answer: c [Reason:] Pectate lyase or pelB protein is produced in plants and helps in degradation of plant cell wall.
8. His tagged proteins can be eluted using EDTA or a pH gradient from the matrix. Is the given statement true or false?
a) True
b) False
Answer
Answer: a [Reason:] His tagged proteins can be eluted using EDTA or a pH gradient from the matrix. They disrupt the chelation.
9. Enterokinase is an intestinal enzyme that converts _______ to ________
a) pepsinogen, pepsin
b) pepsin, pepsinogen
c) trypsinogen, trypsin
d) trypsin, trypsinogen
Answer
Answer: c [Reason:] Enterokinase is an intestinal enzyme which is used to convert inactive trypsinogen to trypsin. It forms the basis for extraction of fusion proteins from the matrix.
10. Cyanogen bromide is used for cleavage of junctions. It cleaves after ________ residues.
a) methionine
b) tryptophan
c) cysteine
d) phenolic acid
Answer
Answer: a [Reason:] Cyanogen bromide is used for cleavage of junctions and it cleaves after methionine residues. But this method is not widely used.
Set 5
1. Gel electrophoresis separates nucleic acid molecules based on:
a) charge on molecules
b) size of the molecules
c) nature of the molecules i.e. whether DNA or RNA
d) chemical properties of the nucleic acids
Answer
Answer: b [Reason:] Gel electrophoresis separates nucleic acid molecules on the basis of their size. The nucleic acid molecules move through the gel because of the force provided by the applied electric field.
2. The charge present on the DNA backbone is negative. The force required to accelerate the molecules towards anode is directly proportional to number of:
a) sugar molecules
b) nitrogenous bases
c) phosphate groups
d) both phosphate group and sugar molecules
Answer
Answer: c [Reason:] The DNA backbone is negatively charged because of the phosphate groups. Hence, the force required to move the molecules towards anode is directly proportional to the number of phosphate groups present.
3. Force is defined as mass per unit acceleration. As the number of phosphate molecules increase, the charge also increases which increases the force required. The acceleration is dependent of the size of the molecules. The given statement is true or false?
a) True
b) False
Answer
Answer: b [Reason:] As the charge increases, which is because of number of phosphate molecules, the size also increases. As, the size increases, it also results in increase of mass. Thus, now the force and also the acceleration are independent of size until a retarding force is present. But, in the case of gel electrophoresis, the retarding force is provided by gel and thus separation takes place on the basis of size.
4. Which one of the following will travel fastest through the gel if the amount of DNA present is same in all?
a) Circular
b) Supercoiled
c) Nicked
d) Supercoiled and circular will move at same speed and faster than nicked
Answer
Answer: b [Reason:] The supercoiled form of DNA will travel the fastest. It is so because; the movement through gel is based on the size. The smaller the molecule is the less retarding force it experiences when it moves. Hence, supercoiled which is having the smallest size will move the fastest.
5. How is the size of molecules under analysis measured?
a) By measuring the distance moved through a ruler
b) By measuring the amount of visualising dye used
c) By running a standard molecule, whose size is known in parallel
d) There is no exact criterion for doing so
Answer
Answer: c [Reason:] The size of the DNA molecules is measured by a standardized molecule. It is known as DNA ladder. The molecules under analysis are compared with the DNA ladder.
6. Gel matrices are generally of two types Agarose and Polyacrylamide. Which of the statements is correct with respect to agarose gels?
a) Agarose is a polysaccharide which is obtained from red algae
b) Agarose is a polysaccharide obtained from fungus
c) It is composed of glucose residues
d) It is obtained via dissolving in it water by boiling in water and then cooling it
Answer
Answer: a [Reason:] Agarose is a polysaccharide which is obtained from red algae. It is composed of galactose residues. Agarose gel is obtained via dissolving in it a buffer by boiling it and then cooling it. It leads to formation of agar in conjunction with other polysaccharide, agropectin.
7. Polyacrylamide gels are the other types of gels which are commonly used. Which of the following statement is not correct with respect to these types of gels?
a) They are obtained via polymerization between acrylamide and bis-acrylamide
b) The components added for initiating polymerization are ammonium persulphate and TEMED
c) It is casted in horizontal and flat trays
d) TEMED catalyses the formation of free radicals from persulphate ions which leads to initiation of cross-linking
Answer
Answer: c [Reason:] Polyacrylamide gels are made up by polymerization of acryl amide and bis acryl amide units. The polymerization takes place because of TEMED and ammonium persulphate, as TEMED catalyses the formation of free radicals from persulphate. These gels are usually casted in vertical trays whereas the agarose gels are casted in horizontal and flat trays.
8. If the amount of agarose added is more, the molecular under analysis should have following characteristsic:
a) small size
b) large size
c) size has no relation with the amount of agarose
d) the amount of molecules under analysis matters
Answer
Answer: a [Reason:] In the case of agrose gels, the separation takes place because of size. If the amount of agarose is more, smaller size molecules will be able to move easily as in comparison to larger size molecules. It is so because; the movement is through the pores. More the amount of agarose, smaller the size of pore.
9. In the case of electrophoresis of single stranded DNA or RNA, which type of gels are used?
a) Renaturing
b) Denaturing
c) The routine agarose gel
d) The routine polyacrylamide gel
Answer
Answer: b [Reason:] In the case of single stranded molecules, denaturing gels are used. It is so because, if denaturing gels are not there, there are chances of formation of secondary structures which hinder the movement of nucleic acids. Thus to avoid this, denaturing agents such as urea etc. are added.
10. At times, a specific fragment of the molecules of DNA which are analyzed needs to be separated. One of the methods is digesting the gels simply. Which of the following statement is not correct in with respect to it?
a) The gelling temperature has an important role to play
b) For higher gelling temperatures, digestion of DNA is done via addition of agarase or some chaotropic agents
c) For lower gelling temperatures, simply slicing out of target DNA is done which is followed by melting
d) The DNA can be extracted via addition of sodium or any positively charged group
Answer
Answer: d [Reason:] For the method of solubilising DNA, gelling temperature is very important. For lower gelling temperatures simply the target DNA can be sliced out and further melting is done. But for higher gelling temperatures, either agarase or chaotropic agents are added. After this, the required DNA is obtained via purification which is done by the addition of silica or solvent extraction can also be done.