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Multiple choice question for engineering

Set 1

1. There are various methods to distinguish whether a colony contains a recombinant or not. One of such method is:
a) blue white screening
b) checking whether replication is taking place or not
c) checking the number of copies
d) looking for the multiple cloning site

View Answer

Answer: a [Reason:] Blue white screening is a method to know whether a colony is having a recombinant or not. It is also known as alpha complementation method. It is based on the lacZ operon. If there is an insert, the colonies are white in colour and if there is no insert, the colonies are blue in colour.

2. At times it is observed that non-recombinant plasmids are more than that of recombinant plasmids. Choose the correct statement in regard to it.
a) It makes easier to get the recombinant plasmids from the mixture
b) The ratio of insert DNA to vector DNA is reduced to get recombinant plasmids
c) Alkaline phosphatase is used to get recombinant plasmids
d) Alkaline phosphatase method is less reliable in comparison to the ratio method

View Answer

Answer: c [Reason:] Often the recombination plasmids are less in number as compared to non-recombination plasmids. This makes it difficult to get the recombination plasmids from the mixture. In order to overcome this, the ratio of insert DNA to vector DNA is increased. Another more reliable method is to use alkaline phosphatase method.

3. Alkaline Phosphatase is used at times and the vector is treated with it. Choose the incorrect statement.
a) It removes 5’ terminal phosphate group from nucleic acids
b) The 5’ phosphate group is required for the ligation to take place
c) Two phosphate bonds should be formed for the complete ligation to take place
d) The ligation between vector and insert won’t take place

View Answer

Answer: d [Reason:] Alkaline phosphatase is used at times and the vector is treated with it. It is responsible for the removal of phosphatase group from the 5’ end. This group is required for the ligation reaction to take place and at each end two phosphates are required. But as the phosphate groups are removed from vector, its relegation is not possible now. But as the insert is still having phosphate group, one strand will form the bond and the ligation reaction will take place.

4. What is the correct time for carrying out the alkaline phosphatase treatment?
a) After the cutting of vector has been done
b) Before the insert DNA and the vector are mixed
c) After the cutting of vector has been done but before the insert DNA and vector are mixed
d) After the mixing of insert DNA and vector

View Answer

Answer: c [Reason:] The alkaline phosphatase treatment is carried out after the cutting of DNA has been done but before the mixing of insert DNA and vector has been done. There should be no traces of the enzyme left after the insert DNA has been added.

5. ccdB gene is used at times. Choose the correct statement in respect to this gene.
a) It is a control of cell birth gene
b) It is activated in complex vectors to increase the fraction of recombinants
c) If intramolecular ligation takes place this protein is released
d) It is often regarded as control of cell death and birth gene

View Answer

Answer: b [Reason:] It is an approach to increase the fraction of recombinants. There are some genes which are activated on the self ligation of the molecules and are responsible for the death of host molecules. ccdB is control of cell death gene and its protein is responsible for killing the host molecules when intramolecular ligation takes place.

6. When inserting a DNA fragment, it is possible to have two orientations. If the orientation is controlled, this cloning is referred to as:
a) forced cloning
b) orientation cloning
c) correct cloning
d) restricted cloning

View Answer

Answer: a [Reason:] It is possible to insert the DNA fragment into two possible orientations. If somehow it is controlled to insert the fragment in a particular orientation, it is known as forced cloning.

7. What happens if insert DNA is cut with two different restriction enzymes at the ends?
a) It is difficult to insert the fragment
b) The insert can be ligated in any orientation
c) The insert can be ligated in one orientation only
d) The amount of product increases

View Answer

Answer: c [Reason:] If the DNA is cut with two different enzymes at the ends, it is possible to ligate the fragment in only one orientation. It is so because each end would have unique sequence to ligate.

8. What is the disadvantage of amplification of using PCR over natural cloning?
a) In PCR, there is no proof reading activity
b) In PCR, small fragments can’t be amplified
c) There is an A incorporated in PCR products, which makes cloning difficult
d) PCR takes more time as compared to natural cloning

View Answer

Answer: a [Reason:] The biggest disadvantage of using PCR amplification over natural cloning is that, there is no proof reading activity in the case of PCR. Thus if an error is induced, it is carried forward and is amplified. Also, if large fragments are to be cloned, natural cloning is preferred over PCR. The incorporated A at ends, makes the process of cloning of PCR products easier.

9. TA cloning is a method used for cloning of PCR products. Which of the statement is correct with respect to it?
a) It is based on the fact that a T residue is incorporated at the end of the PCR product
b) ‘A’ residue is incorporated into the end of the vector
c) It gives low yield
d) It is preferred over blunt end ligation

View Answer

Answer: d [Reason:] TA cloning is a method used for cloning of PCR products. It is based on the fact that A residue is present at the 3’ end of the PCR product and thus now T residue is incorporated at the end of the vector. It is preferred over blunt end ligation.

10. Choose the incorrect statement in respect to topoisomerase I.
a) It is used to cleave only one DNA strand
b) It cleaves at the recognition sequence –C/TCCTT- and is covalently attached to one end of the cleaved molecule
c) The supercoiling of the DNA strand is altered and then it is sealed again by the enzyme
d) It is slower than the normal DNA ligase

View Answer

Answer: d [Reason:] Topoisomerase I is enzyme used for cleaving of one DNA strand. It cleaves at the recognition sequence –C/TCCTT- and is covalently attached to one end of the cleaved molecule. The supercoiling of the DNA strand is altered and then it sealed by the enzyme again. It is usually faster than the DNA ligase. Topoisomerase II is used for cleaving both the strands.

11. Linkers are often used in cloning. Choose the incorrect statement for linkers.
a) These are short chemically synthesized molecules that contain a particular restriction enzyme site within the sequence
b) They are blunt ended molecules
c) They are ligated to staggered ended insert molecules by T4 DNA ligase
d) After treatment with enzyme, both the ends of the linker are staggered

View Answer

Answer: c [Reason:] Linkers are often used in cloning. These are short chemically synthesized molecules that contain a particular restriction enzyme site within the sequence. They are blunt ended molecules and are ligated to the blunt ended insert molecules by T4 DNA ligase. After treatment with enzyme, both the ends of the linker are staggered.

12. There is no effect if the insert itself contains the restriction site. The given statement is true or false?
a) True
b) False

View Answer

Answer: b [Reason:] If the insert itself is having a restriction site, the insert itself is cleaved when the restriction enzyme is cleaved along with the linker. To avoid this, methylation of the site in the insert is done.

13. Choose the correct statement for adaptors.
a) They are blunt ended at both the ends
b) They are single stranded at both the ends
c) They may be single stranded at one end and other end may be blunt
d) They don’t have extra restriction sites within their sequence

View Answer

Answer: c [Reason:] Adaptors are molecules which are used for cloning. There is no restriction on the type of the end they have. Either of the ends can be blunt or staggered. They may also have extra restriction site within the sequence.

14. If linkers are combined with other features such as a selectable marker, it is called as:
a) cassette
b) modified linker
c) adaptors
d) induced linker

View Answer

Answer: a [Reason:] If linkers are combined with the features such as antibiotic resistance, these are called as cassette or cloning catridges. They may also contain gene expressing signals.

Set 2

1. What are the possibilities which can occur until the temperature has reached for primer annealing?
a) Extension doesn’t starts until the appropriate temperature is reached
b) Extension may start even when the temperature is low
c) At low temperature, there is specific annealing of primer taking place
d) There are more specific products which are generated

View Answer

Answer: b [Reason:] Until the temperature has reached for primer annealing there are chances of extension by polymerase. It is so because at low temperatures primer can anneal in a non specific manner and thus non specific products are generated.

2. Hot-start PCR is a modification of PCR. Which of the following is not corresponding to it?
a) The basis is that extension is not started until the first cycle reaches its maximum temperature
b) The polymerase is added after the first cycle has reached its maximum temperature or melting temperature
c) It is satisfactory for small number of samples
d) It leads to generation of non specific products

View Answer

Answer: d [Reason:] Hot-start PCR is a modification which is used in order to overcome the problem of extension before the maximum temperature of first cycle is reached. Hence, polymerase is added only after the maximum temperature for first cycle is reached. Hence, there are more specific products which are generated because proper annealing of primers has taken place. It is suitable for small number of samples but not for large number of samples.

3. An alternative to adding polymerase at later stage is:
a) Make the polymerase inactive by binding it to an antibody
b) Introduce the polymerase or Magnesium in clay beads
c) Make the polymerase inactive by attaching groups which cause stearic inhindrance
d) Introduction of polymerase or Magnesium in plastic wires

View Answer

Answer: a [Reason:] An alternative to start the extension at higher temperature is to make the polymerase inactive by binding an antibody to it. The antibody detaches itself at higher temperature and thus polymerase is activated at higher temperature. Also, the polymerase or Magnesium can be introduced into wax beads and these beads melt at higher temperatures. Magnesium is required for the polymerase to function.

4. The primer annealing temperature is often very low from the maximum temperature. This low temperature leads to some mismatches. Is the statement true or false?
a) True
b) False

View Answer

Answer: a [Reason:] The primer annealing temperature is often very low from the maximum temperature. Though the low temperature is for stable binding of the template and the primer but at times it leads to mismatches.

5. Touch-down PCR is another modification. Its characteristics include:
a) Lowering the temperature for primer annealing
b) Primer annealing is done at higher temperatures initially
c) The temperature is abruptly reduced in the second cycle
d) In earlier cycles less stringent conditions are there and in later cycles more stringent conditions are there

View Answer

Answer: b [Reason:] It is done in order to overcome the slight mismatch which takes place at lower temperatures. For this, initially the temperature is kept very high and it is reduced in further cycles. As the temperature is reduced, a stage is reduced at which correct primer-template binding is possible but not the incorrect one. In this, in the earlier cycles more stringent conditions are there and in later cycles less stringent conditions are there.

6. If two successive PCR are carried out, it is called as:
a) Touch-down PCR
b) Hot-start PCR
c) Combined PCR
d) Nested PCR

View Answer

Answer: d [Reason:] Nested PCR is that in which two PCRs are carried out. In the first PCR, it uses a conventional template and the second PCR is carried out using the product of first PCR as a template.

7. If two successive PCRs are carried out, in which PCR there are chances of having a non-specific product?
a) First PCR
b) Second PCR
c) Both the PCRs
d) It depends on the annealing temperature

View Answer

Answer: a [Reason:] If two successive PCRs are carried out, there are non-specific products created in the first PCR. But there are least chances that non-specific products also have annealing sites for both the primers in the second PCR. Hence, non specific products are not generated in second PCR.

8. The process of inserting an amplified PCR product in a vector for cloning is known as:
a) making library
b) insertion
c) making a hard copy
d) making a PCR based vector

View Answer

Answer: c [Reason:] The process of inserting an amplified PCR product in a vector for cloning is termed as making a hard copy. It is further maintained by conventional means.

9. How can PCR product be cloned into a vector?
a) It can be done only when PCR products are blunt-ended
b) It can be done only by restriction enzyme digestion
c) Both the methods can be used
d) The blunt-ended approach is favoured

View Answer

Answer: b [Reason:] PCR product can be cloned into a vector if the DNA molecules are blunt ended or it can also be done by restriction enzyme digestion. In restriction enzyme digestion restriction sites are introduced.

10. Which of the following statement is incorrect regarding cloning of PCR products?
a) In cloning via restriction enzymes, restriction sites are induced before amplification is carried out
b) The restriction sites are induced in the primers before annealing
c) The intermediate molecules are having restriction sites at both ends
d) The amplified molecules can be cut at both the ends by appropriate enzymes

View Answer

Answer: c [Reason:] If cloning is done via restriction enzymes, restriction sites are induced before amplification. The restriction sites are induced in the primers before annealing. As the primer binds, the restriction sites are induced at one end of intermediate molecule. In full length molecules, restriction sites are at both the ends. And the amplified molecules can be cut at both the ends by appropriate enzymes.

11. Topoisomerse I is also used for cloning of PCR product at times. Which of the statement holds true for such type of cloning?
a) The restriction site is induced into the vector and the topisomerase enzyme is induced into the PCR primers
b) The topoismerase I is used for cutting both the strands
c) The induction of topoisomerase enzyme is done into the vector in the case it is very small in size
d) The restriction site is induced into the PCR primers and the topoisomerase enzyme is induced into the vector

View Answer

Answer: d [Reason:] In the case of this type of cloning, the restriction site is induced into the PCR primers and the enzyme is induced into the vector. The enzyme cuts the PCR product at the restriction site and joins it to the vector. Topoisomerase I is responsible for cutting only one strand and Topoisomerase II cuts both the strands.

12. Generally, amplification is carried out between the PCR primers. But if amplification is carried out outside the primers, it is called as:
a) Inverse PCR
b) Circular PCR
c) Non-conventional PCR
d) In-situ PCR

View Answer

Answer: a [Reason:] Generally, the amplification is carried out of the region which is flanked by the primers. But in inverse primers amplification is carried out of the region which lies outside the primers.

Set 3

1. Mitochondrial genome encodes tRNAs, _____ and polypeptides involved in _______
a) mRNAs, oxidative phosphorylation
b) rRNAs, oxidative phosphorylation
c) rRNAs, reductive phosphorylation
d) mRNAs, reductive phosphorylation

View Answer

Answer: b [Reason:] Mitochondrial genome encodes tRNAs, rRNAs and polypeptides which are required for oxidative phosphorylation. tRNAs and rRNAs are also encoded by chloroplast genome.

2. Atrazine is a herbicide and it acts on:
a) reaction centre in photosystemI
b) reaction centre in photosytemII
c) reaction centre in both the photosystems
d) neither of the photosystems

View Answer

Answer: b [Reason:] Atrazine is a herbicide and it acts on a reaction centre present in photosystem II. This herbicide is a product of chloroplast psbA gene.

3. Allotopic gene expression is the case when the presence of a normal gene in an organelle is not a problem in expression. Is the given statement true or false?
a) True
b) False

View Answer

Answer: a [Reason:] At times, the presence of normal gene in the organelle doesn’t creates a problem and thus inserting modified organelle genes into the nucleus may be expressed well. Such expression is called as allotropic gene expression.

4. atpB encodes _______ subunit of ATPsynthase, an enzyme used for generation of ______
a) beta, ADP
b) alpha, ATP
c) beta, ATP
d) alpha, ADP

View Answer

Answer: c [Reason:] atpB encodes beta subunit of ATPsynthase, it is a multisubunit complex used for generation ATP and it is done in the presence of light reaction.

5. Bacterial aadA gene is responsible for conferring resistance to:
a) spectinomycin
b) streptomycin
c) ampicillin
d) spectomycin and streptomycin

View Answer

Answer: d [Reason:] Bacterial aadA gene is responsible for conferring resistance to both streptomycin and spectomycin. It is used a selectable marker for chloroplast transformation.

6. How many types of chloroplast are there in Chlamydomonas?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: a [Reason:] Chlamydomonas is having only one type of chloroplast and this property makes it easier to use it for transformation.

7. For transformation of chloroplast of higher plants, a vector is used which ______ in the chloroplast.
a) doesn’t replicates
b) replicates
c) may or may not replicate
d) replicates under certain specified conditions

View Answer

Answer: a [Reason:] For transformation of chloroplast of higher plants, a vector is used which doesn’t replicates in the chloroplast. There is a selectable marker which is present and the gene of interest is flanked by chloroplast DNA.

8. Chloroplast can be transferred through pollen in all crops. Is the given statement true or false?
a) True
b) False

View Answer

Answer: b [Reason:] Cholorplast can’t be transferred through pollen for all the crops. Thus incorporation of transgenes in chloroplast may offer more biological containment then that incorporation into nucleus may offer.

9. Mutant strains of Saccharomyces cervevisiae in which endogenous DNA are deleted are called as:
a) rho0
b) synthetic rho
c) rho+
d) rho-

View Answer

Answer: a [Reason:] Mutant strains of Saccharomyces cervevisiae in which endogenous DNA are deleted are called as rho0. Synthetic rho- strains are produced when DNA is introduced into mitochondria and concatamers are produced.

10. COX3 gene is a selectable marker. Choose the correct statement with respect to it.
a) It confers the ability to grow by anaerobic respiration
b) It confers the ability to grow by aerobic respiration
c) It confers the ability to grow in absence of uracil
d) It confers the ability to grow in lithium acetate medium

View Answer

Answer: b [Reason:] COX3 gene is used as a selectable marker. It confers the ability to grow by aerobic respiration in the mutant cells for mitochondrial COX3 gene.

11. The ARG8m gene which produces an enzyme for arginine biosynthesis is located in _______ and is of ______ origin.
a) mitochondrial, nuclear
b) nuclear, mitochondrial
c) nuclear, nuclear
d) mitochondrial, mitochondrial

View Answer

Answer: a [Reason:] The ARG8m gene which produces an enzyme for arginine biosynthesis is located in the mitochondria but is of nuclear origin. It is designed for expression in the mitochondrion and will confer the ability to grow in the absence of arginine.

12. Barstar is:
a) RNAse
b) RNAse inhibitor
c) DNAse
d) DNAse inhibitor

View Answer

Answer: b [Reason:] Barstar is RNAse inhibitor. And Barsar is RNAse and inhibitor is used as a selectable marker. Barsar is used for degrading the mitochondrial RNA. Barstar added helps in suppressing the function of Barsar and thus restoration of mitochondrial function takes place.

13. Caenorhabditis elegans is a model organism of great importance in biological systems. It is a/an:
a) algae
b) parasite
c) fungi
d) nematode

View Answer

Answer: d [Reason:] Caenorhabditis elegans is a model organism of great importance in biological systems and it is a nematode. The genetic manipulation of the organism is quite complex.

14. DNA can be injected into Caenorhabditis elegans by biolistic transformation. The injected DNA forms arrays of extrochromosomal copies which are stable in nature. Is the given statement true or false?
a) True
b) False

View Answer

Answer: b [Reason:] DNA can be injected into Caenorhabditis elegans by biolistic transformation. The injected DNA forms extrachromosomal copies but these are not stable in nature. This can be avoided by the incorporation of poison sequences.

Set 4

1. Basic classification of polymerases includes how many types?
a) 2
b) 3
c) 4
d) 5

View Answer

Answer: d [Reason:] The types are- DNA dependent DNA polymerase, DNA dependent RNA polymerase, RNA dependent DNA polymerase, template independent polymerase and RNA dependent RNA polymerase. Out of these, RNA dependent RNA polymerases are not focused so much in comparison to other polymerases.

2. Polymerase can be defined as:
a) an enzyme used to synthesize a new DNA or RNA strand on the basis of pre-existing strand or at times without a pre-existing strand
b) an enzyme used for removal of nucleotides from the DNA or RNA strand
c) an enzyme which can synthesize only a new DNA strand, not a RNA strand
d) an enzyme which can synthesize either a new DNA or a RNA strand but only when a strand is there

View Answer

Answer: a [Reason:] The synthesis of a new DNA or RNA strand can be done either on the basis of a pre-existing strand or without it. Those which don’t require a pre-existing strand are known as template free or template independent.

3. Which of the following activity is not possible in the case of DNA polymerase I?
a) 3’-5’ exonuclease
b) 5’-3’ exonuclease
c) 5’-3’ DNA synthesis
d) 3’-5’ DNA synthesis

View Answer

Answer: d [Reason:] DNA polymerase is having ability to synthesize DNA strand in 5’-3’ direction but not in 3’-5’ direction. Also, it is having exonuclease activity in both the directions, which means that it can remove bases in either of the direction but can synthesize only in 5’-3’ direction.

4. The E. coli DNA polymerase enzyme gives different domains with different activities on cleaving with protease subtilisin. Which of the following statements is correct with respect to the fragments generated?
a) The smaller fragment is having C terminal and the larger fragment is having N terminal
b) The smaller fragment is named as Klenlow fragment and the intact molecule is called as Kornberg fragment
c) The smaller fragment is having 5’-3’ exonuclease activity whereas the larger fragment is having 5’-3’ polymerase and 3’-5’ exonuclease activity
d) Both the fragments are having 5’-3’ polymerase and 3’-5’ exonuclease activity

View Answer

Answer: c [Reason:] The two fragments are generated of size 35kDa and 76kDa, with the N terminal in the smaller fragment. The larger fragment, which is of 76kDa is known as Klenlow fragment and the intact molecule is called Kornberg fragment. The smaller fragment is having 5’-3’ exonuclease activity whereas the larger fragment is having 5’-3’ polymerase and 3’-5’ exonuclease activity.

5. Removal of single stranded portions produced due to exonucleolytic activity and due to polymerase activity are termed as:
a) polishing and end filling respectively
b) end filling and polishing respectively
c) polishing in both the cases
d) end filling in both the cases

View Answer

Answer: a [Reason:] The single stranded ends generated due to exonucleolytic activity can either be removed by generating their complementary strand or removing the single stranded overhang. In both the cases, it is termed as polishing. Whereas removal of single stranded regions generated because of polymerase activity is termed as end-filling.

6. Thermostable DNA polymerases are very important in PCR. How are they obtained?
a) They are obtained by heating the bacteria manually over high temperatures
b) They are isolated from extremely stable thermophilic bacteria which are often found growing in oceanic vents
c) They are found everywhere in the nature
d) They are obtained by genetically modifying the E. coli bacteria with thermal stability property

View Answer

Answer: b [Reason:] Thermostable DNA polymerases are found naturally in thermophilic bacteria which can be found growing in oceanic vents. They are having high stability and their DNA polymerases can function effectively even at high temperatures in-vitro.

7. Which of the following enzyme is said as reverse transciptase?
a) DNA dependent DNA polymerase
b) RNA dependent RNA polymerase
c) RNA dependent DNA polymerase
d) DNA dependent RNA polymerase

View Answer

Answer: c [Reason:] RNA dependent DNA polymerases are said as reverse transciptase and the function follows it name. The function is to reverse the phenomenon of general transcription, in which RNA is synthesized from DNA. But here it is reversed and DNA is synthesized by using RNA as a template.

8. Why reverse transciptase enzymes are having comparatively high error rates than other polymerases?
a) Because they are not having 3’-5’ proofreading exonucleolytic activity
b) Because they are not having 5’-3’ proofreading exonucleolytic activity
c) Because they are having slow rates of exonucleolytic activity
d) It is difficult to synthesize DNA from RNA

View Answer

Answer: a [Reason:] Reverse transciptase enzymes are not having proof reading exonuclease activity in 3’-5’ direction. Hence, when the synthesis is done in 5’-3’ direction it is not checked in the 3’-5’ direction and thus the errors inculcated won’t be removed.

9. Which polymerase can be used in conjunction with appropriate phage promoters in order to have high levels of specific transcription?
a) RNA dependent DNA polymerase
b) DNA dependent RNA polymerase
c) RNA dependent RNA polymerase
d) DNA dependent DNA polymerase

View Answer

Answer: b [Reason:] DNA dependent RNA polymerases are very specific for phage promoters and thus they are used for carrying out highly specific transcription. They are often isolated from T3, T7 phages.

10. Template independent polymerases are the enzymes which add nucleotide bases without a template. Which of the following statements is correct with respect to these?
a) They only add a single nucleotide
b) They only add a string of nucleotides and not a single nucleotide
c) Terminal transferase adds a series of nucleotides at the 3’ end
d) Taq polymerase adds a single nucleotide at the 5’ end of the PCR product

View Answer

Answer: c [Reason:] Template independent polymerases can either add a single nucleotide or a series of nucleotides; it is based on the template. Terminal transferase adds a series of nucleotides at the 3’ end, which generates a single stranded tail. Whereas, Taq polymerase adds a single A base at 3’ end of the PCR product.

Set 5

1. If methods are based on cellular processes that lead to inactivation of gene expression by affecting the RNA, then it is called as:
a) transcriptional
b) pre-transcriptional
c) post-transcriptional
d) translational

View Answer

Answer: c [Reason:] If inactivation of gene expression is carried out by affecting the RNA then these methods are referred as post-transcriptional. As transcription is the process of obtaining RNA from DNA.

2. Choose the incorrect statement for the method based on antisense RNA.
a) RNA is synthesized complementary to the sequence of the gene which is to be inactivated
b) It is achieved by placing a DNA sequence which encodes RNA complementary to the RNA to be inactivated
c) Expression of the endogenous gene is diminished
d) This method is preferred over gene disruption has gene inactivation can be achieved completely

View Answer

Answer: d [Reason:] Antisense RNA is the RNA which is complementary to the RNA sequence which is to be inactivated. It is done with the help of a DNA sequence. Expression of the endogenous gene is diminished. This method doesn’t leads to complete inactivation, which is not the case with gene disruption.

3. The method of post transcriptional gene silencing is particularly useful in:
a) plants
b) animals
c) insects
d) microorganisms

View Answer

Answer: a [Reason:] The method of post transcriptional gene silencing is particularly useful in plants.

4. Down regulation of expression of endogenous genes by transformation with constructs that would generate sense RNA, rather than anti-sense RNA is known as:
a) suppression
b) co-suppression
c) multisuppression
d) anti-suppression

View Answer

Answer: b [Reason:] When anti-sense RNA is used in plants, a phenomenon observed is co-suppression. It is the down regulation of expression of endogenous genes by transformation with constructs that would generate sense RNA, rather than anti-sense RNA.

5. In some organisms, presence of double stranded RNAs leads to breakdown of corresponding single stranded mRNA. Is the given statement true or false?
a) True
b) False

View Answer

Answer: a [Reason:] In some organisms, presence of double stranded RNAs leads to breakdown of corresponding single stranded endogenous mRNA. The double stranded RNA is having one strand same as that of endogenous RNA.

6. Double stranded RNA is cleaved by a nuclease called as Dicer and small fragments are generated known as:
a) short interfering RNAs
b) long interfering RNAs
c) short interspersed RNAs
d) long interspersed RNAs

View Answer

Answer: a [Reason:] Double stranded RNA is cleaved by a nuclease called as Dicer and small fragments are generated, they are about 22 nucleotides long and are known as short interfering RNAs (siRNA).

7. The process of RNA inactivation by siRNAs is termed as:
a) RNA silencing
b) RNA interference
c) Short RNA inactivation
d) RNA disfunction

View Answer

Answer: b [Reason:] siRNAs are short interfering RNAs. The process of RNA inactivation by use of these is called as RNA interference (RNAi).

8. DNA _________ is also a method for gene silencing through short RNAs.
a) acetylation
b) phosphorylation
c) methylation
d) acylation

View Answer

Answer: c [Reason:] Short RNAs can also lead to gene silencing via DNA methylation.

9. siRNAs can either be introduced directly or by microinjection. Is the given statement true or false?
a) True
b) False

View Answer

Answer: a [Reason:] siRNAs can either be introduced directly or by microinjection. It can also be induced by feeding as in the case of C. elegans.

10. Introduction into host organism can also be done by using a DNA construct, which when transcribed, generates a RNA which is _________
a) circular
b) linear
c) double stranded
d) self-complementary

View Answer

Answer: d [Reason:] Introduction into the host organism can also be done by using a DNA construct, which when transcribed, generates a RNA which is self-complementary. It leads to formation of double stranded RNA and is capable of activating RNAi effect.