Q.1. Following statements describe the characteristics of the enzyme restriction endonuclease. Identify the incorrect statement. (2019)
(a) The enzyme recognises a specific palindromic nucleotide sequence in the DNA.
(b) The enzyme cuts DNA molecule at identified position within the DNA.
(c) The enzyme binds DNA at specific sites and cuts only one of the two strands.
(d) The enzyme cuts the sugar-phosphate backbone at specific sites on each strand.
The restriction endonuclease enzyme inspects the length of a DNA sequence. Once it recognises specific sequence, it binds to the DNA and cuts each of the two strands of the double helix at specific points in their sugar phosphate backbone. Special sequence in the DNA recognised by restriction endonuclease is called palindromic nucleotide sequence.
Q.2. DNA precipitation out of a mixture of biomolecules can be achieved by treatment with (2019)
(a) Chilled chloroform
(c) Chilled ethanol
(d) Methanol at room temperature
In order to cut the DNA with restriction enzymes, it needs to be in pure form, free from other macromolecules. Since the DNA is enclosed by the membranes, we have to break the cell open to release DNA and other macromolecules like RNA, proteins, polysaccharides and lipids. It is obtained by treating the bacterial cells/plant or animal tissue with enzymes. Other molecules are removed by appropriate treatments and purified DNA ultimately precipitates out after the addition of chilled ethanol.
Q.3. Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes? (2019)
(b) BOD incubator
(c) Sludge digester
(d) Industrial oven
Q.4. A selectable marker is used to: (2019)
(a) Help in eliminating the non-transformants, so that the transformants can be regenerated
(b) Identify the gene for a desired trait in an alien organism
(c) Select a suitable vector for transformation in a specific crop
(d) Mark a gene on a chromosome for isolation using restriction enzyme
Q.5. Given below are four statements pertaining to separation of DNA fragments using gel electrophoresis. Identify the incorrect statements.
(i) DNA is negatively charged molecule and so it is loaded on gel towards the anode terminal.
(ii) DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA.
(iii) Smaller the size of DNA fragment larger is the distance it travels through it.
(iv) Pure DNA can be visualized directly by exposing UV radiation.
Choose correct answer from the options given below
(a) (i), (iii) and (iv)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iv)
Q.6. The correct order of steps in Polymerase Chain Reaction (PCR) is
(a) Extension, denaturation, annealing
(b) Annealing, extension, denaturation
(c) Denaturation, extension, annealing
(d) Denaturation, annealing, extension
A single PCR amplification cycle involves three basic steps, denaturation heating of target DNA to high temperature resulting in separation of two strands, annealing two oligonucleotide primers anneal or hybridise to each single template DNA and extension. Taq DNA polymerase synthesises DNA between primers and primers extend towards each other such that DNA stranded segment lying between the two is copied.
Q.7. The DNA fragments separated on an agarose gel can be visualised after staining with (2017)
(b) Aniline blue
(c) Ethidium bromide
(d) Bromophenol blue
The separated DNA fragments can be seen only after staining them with a compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange coloured bands.
Q.8. DNA fragments are (2017)
(a) Negatively charged
(c) Either positively or depending on their size
(d) Positively charged
Q.9. A gene whose expression helps to identify transformed cell is known as (2017)
(c) Structural gene
(d) Selectable marker
Some genes called “selectable markers” help in selecting those host cells which contain the vectors (transformants) and eliminating the non-transformants.
Q.10. What is the criterion for DNA fragments movement on agarose gel during gel electrophoresis? (2017)
(a) The smaller the fragment size, the farther it moves.
(b) Positively charged fragments move to farther end.
(c) Negatively charged fragments do not move.
(d) The larger the fragment size, the farther it moves.
Electrophoresis is a technique used for the separation of substances of different ionic properties. Since the DNA fragments are negatively charged molecules, they can be separated by allowing them to move towards the anode. DNA fragments move towards the anode according to their molecule size through the pores of agarose gel. Thus, the smaller fragments move farther away as compared to larger fragments.
Q.11. The process of separation mid purification of expressed protein before marketing is called (2017)
(a) Downstream processing
(c) Postproduction processing
(d) Upstream processing
After the formation of the product in the bioreactor it undergoes some processes before a finished product is ready for marketing. The process includes separation and purification of products which are collectively called downstream processing.
Q.12. Stirred-tank bioreactors have been designed for (2016)
(a) Purification of product
(b) Addition of preservatives to the product
(c) Availability of oxygen throughout the process
(d) Ensuring anaerobic conditions in the culture vessel
A stirred-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates, even mixing and oxygen availability throughout the biorcactor.
Q.13. A foreign DNA and plasmid cut by the same restriction endonuclease can be joined to form a recombinant plasmid using
(b) Taq polymerase
(c) Polymerase III
Ligase is a class of enzymes that catalyse the formation of covalent bonds using the energy released by the cleavage of ATP. Ligases arc important in the synthesis and repair of many biological molecules, including DNA ligase and used in genetic engineering to insert foreign DNA into cloning vectors.
Q.14. Which of the following is not a component of downstream processing? (2016)
After the formation of the product in bioreactor, it undergoes some processes before a finished product to be ready for marketing. Downstream processing includes separation and purification process. The product obtained is subjected to quality' control, testing and kept in suitable preservatives.
Q.15. Which of the following restriction enzymes produces blunt ends? (2016)
(a) Sal I
(b) Eco RV
(c) Xho I
(d) Hind III
EcoRV is a type II restriction endonuclease isolated from certain strains of E.coli. It creates blunt ends. It recognises the palindromic sequence of 6 bases. Sal I, Xho I and Hind lll restriction enzymes produce sticky ends.
Q.16. Which of the following is not a feature of the plasmids? (2016)
(c) Independent replication
(d) Circular structure
Plasmids are extra-chromosomal, self- replicating, usually circular, double-stranded DNA molecules that serve as vectors which carry foreign DNA segment and replicate inside host cell.
Q.17. The Taq polymerase enzyme is obtained from (2016)
(a) Bacillus subtilis
(b) Pseudomonas putida
(c) Thermus aquaticus
(d) Thiobacillus ferroxidans
Tag polymerase, generally used in PCR is isolated from thermophilic bacterium Thermus aquaticus.
Q.18. Which of the following is a restriction endonuclease? (2016)
(a) DNase I
(c) Hind ll
Hind II is the first restriction endonuclease. It was isolated from Haemophilus influenzae Rd. It always cut DNA at specific position producing blunt ends. DNase I is an endonuclease that cleaves DNA preferentially at phosphodiester linkages adjacent to a pyrimidine nucleotide. RNase is a type of nuclease that catalyses the degradation of RNA into smaller components. It can be endoribonuclease or exoribonuclease. A protease is an enzyme that perform proteolysis, i.e., protein catabolism by hydrolysis of the peptide bonds.
Q.19. Which of the following is not required for any of the techniques of DNA fingerprinting available at present? (2016)
(a) Restriction enzymes
(b) DNA-DNA hybridisation
(c) Polymerase chain reaction
(d) Zinc finger analysis
Any small, functional, freely folded domain in which coordination of one or more zinc ions is required to stabilise its structure is known as zinc finger. The z.inc finger domains are widely dispersed in eukaryotic genomes and are actively involved in sequence specific binding to DNA/RNA and contribute in protein-protein recognitions.
Q.20. Which of the following is not a feature of the plasmids? (2016)
(a) Independent replication
(b) Circular structure
(d) Single - stranded
Plasmid has an extra chromosomal, double stranded circular DNA.
Q.21. The taq polymerase enzyme is obtained from (2016)
(a) Thermus aquaticus
(b) Thiobacillus ferroxidans
(c) Bacillus subtilis
(d) Pseudomonas putida
The Taq polymerase enzyme is obtained from Thermus aquaticus which lives in hot springs
Q.22. Which of the following is a restriction endonuclease? (2016)
(a) Hind II
(c) DNase I
A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Hind II among these is a type of restriction endonuclease.
Q.23. The cutting of DNA at specific locations became possible with the discovery of (2015)
(b) Selectable markers
(d) Restriction enzymes
Restriction enzymes are used to cut DNA at specific locations
Q.24. The DNA molecule to which the gene of interest is integrated for cloning is called: (2015)
A vector is a DNA molecule which is used as a vehicle to carry the gene of interest to another cell
Q.25. An analysis of chromosomal DNA using the Southern hybridization technique does not use: (2014)
PCR is a technique for enzymatically replicating DNA without using a living organism such as E. coli or Yeast. It is commonly used in medical and biological research labs for a variety of tasks like detection of hereditary diseases, identification of genetic fingerprints etc.
Q.26. In vitro clonal propagation in plants is characterized by: (2014)
(a) PCR and RAPD
(b) Northern blotting
(c) Electrophoresis and HPLC
Now a days PCR and RAPD technique are used for the characterisation of in vitro clonal propagation in plants.
Q.27. Which vector can clone only a small fragment of DNA? (2014)
(a) Bacterial artificial chromosome
(b) Yeast artificial chromosome
Plasmids are small extranuclear circular DNAs which carry extrachromosomal genes in bacteria and some fungi. They replicate independently. The best known vectors which are also available commercially are pBR322 and pUC-18.