DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as: [NEET 2021]
The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation (you cannot see pure DNA fragments in the visible light and without staining). You can see bright orange coloured bands of DNA in a ethidium bromide stained gel exposed to UV light.
Genes of interest can be selected from a genomic library by using
[NEET Kar. 2013]
A hybridization probe is a fragment of DNA of variable length which is used in DNA samples to detect the presence of nucleotide sequence (the DNA target) that are complementary to the sequence in the probe. The probe hybridize to single–stranded DNA whose base sequence allow probe target base-pairing due to complementary between the probe and target.
The colonies of recombinant bacteria appear white in contrast to blue colonies of non recombinant bacteria because of :
Blue-white screening allows detecting rapidly the recombinant bacteria in vector-based cloning experiments. The blue-white screening method works by disrupting the α-complementation process. The plasmid carries within the lacZ α sequence an internal multiple cloning site or MCS.
This MCS can be cut by restriction enzymes so that the foreign DNA may be inserted, thereby disrupting the gene and production of α-peptide. Consequently, in cells containing the plasmid with an insert, no functional β-galactosidase may be formed. The presence of an active β-galactosidase can be detected by X-gal, a colourless analogue of lactose, that may be cleaved to form a bright blue insoluble pigment.
This results in a characteristic blue colour in cells containing the functional β-galactosidase. Blue colonies, therefore, show that they may contain a vector, while white colonies indicate the presence of an insert in lacZ α which disrupts the formation of an active β-galactosidase.
DNA fragments generated by the restriction endonucleases in a chemical reaction can be separated by :
DNA fragments generated by restriction endonucleases in a chemical reaction can be separated by gel electrophoresis. Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. The DNA fragments separate according to their size through sieving effect provided by matrix.
Which one of the following represents a palindromic sequence in DNA?
A palindromic sequence is a nucleic acid sequence (DNA or RNA) that is the same whether read 5' (five-prime) to 3' (three prime) on one strand or 5' to 3' on the complementary strand with which it forms a double helix.
5. - GAATTC - 3.
3. - CTTAAG - 5.
It is a palindromic sequence of DNA cut by restriction enzyme ECORI.
The figure below shows three steps (A, B, C) of Polymerase Chain Reaction (PCR). Select the option giving correct identification together with what it represents?
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.
The correct steps shown in the above figure are:
A – Denaturation at a temperature of about 94° to 98°C. During the denaturation, the double strand melts open to single stranded DNA, and all enzymatic reactions stop.
B – Annealing (binding of DNA primer to the separated strands. Occurs at 50° to 65°Celsius, which is lower than the optimal temperature of the DNA polymerases) C – Extension or elongation of the strands using the DNA primer with heat-stable DNA polymerases, most frequently Taq (Thermus aquaticus) at 72ºC.
In genetic engineering, the antibiotics are used
Antibiotics are powerful medicines that fight bacterial infections. They either kill bacteria or keep them from reproducing. In genetic engineering, the antibiotics are used as selectable markers.
Biolistics (gene-gun) is suitable for
Biolistic it is direct gene transfer red method for constructing recombinant DNA. The gene gun was invented by John C. Sanford with Edward Wolf. A gene gun can be used to genetically infect cells or whole organisms with foreign DNA by aiming the barrel of the gun and firing. The microshot projectiles in the biolistic gene gun are made of microscopic (or nano) sized gold or platinum powders. These expensive powders are soaked in DNA or RNA (in raw or plasmid form) that are engineered for insertion into the genome of the cells or organisms under the gun.
For transformation, micro-particles coated with DNA to be bombarded with gene gun are made up of :
For gene transfer in to the host cell without using vector microparticles made of tungsten and Gold coated with foregin DNA are bombarded into target cells at a very high velocity.
Which one is a true statement regarding DNA polymerase used in PCR
The name of this DNA polymerase is Taq polymerase extracted from a thermophilic bacterial.
A single strand of nucleic acid tagged with a radioactive molecule is called :
A single strand DNA or RNA tagged with radioactive molecule that is used in of hybridization of DNA or RNA is called probe.
PCR and Restriction Fragment Length Polymorphism are the methods for :
PCR and RFLP are the methods used for genetic fingerprinting. DNA fragmentation plays an important part in forensics, especially that of DNA profiling. Restriction fragment length polymorphism (RFLP) analyses the variable lengths of DNA fragments which are formed from the digestion of a DNA sample with a restriction endonuclease. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. In polymerase chain reaction (PCR), This sample DNA is amplified from a single copy to millions of copies of DNA. It used to amplify a specific region of a DNA strand. Most PCR methods amplify DNA fragments of between 0.1 and 10 kilo base pairs (kb), although some techniques allow amplification of fragments up to 40 kb in size.
The figure below is the diagrammatic representation of the E.Coli vector pBR 322. Which one of the given options correctly identifies its certain component (s) ?
In pBR 322
ori - represents site of originor replication rop-represents those proteins that take part in replication of plasmid. Hind III, EcoRI- Recoginition sites of Restriction endonucleases ampR and tetR - They are antibiotic resistant gene part
Bacillus thuringiensis forms protein crystals which contain insecticidal protein.
Bacillus thuringiensis produces a large amount of crystalline protein during sporulation. In the cell toxins are formed along with the spore and are referred to as parasporal body. The bacteria are capable of entering the insect’s blood and using the host insect to reproduce. The proteins from ingested spores are activated by gut, high pH and the polypeptide toxins destroy gut epithelial cells and kill the pest.
Agarose extracted from sea weeds finds use in :
In gel electrophoresis agarose extracted from sea weed used as gel garose, made of 0.7% gel show good resolution of large DNA and 2% gel will show good resolution of small fragments.
There is a restriction endonuclease called EcoRI. What does .co. part in it stand for ?
EcoRI is an endonuclease enzyme isolated from strains of E.coli and a part of restriction modified system. So co part stands for coli.
Restriction endonucleases are enzymes which
Restriction endonucleases are enzymes that makes cuts at specific positions within the DNA molecule. They acts as molecular scissors. They recognise specific base sequence at palindrome sites in DNA duplex and cut its strands.
DNA or RNA segment tagged with a radioactive molecule is called
DNA or RNA segment tagged with a radioactive molecule is called Probe. They are used to detect the presence of complementary sequences in nucleic acid samples. Probes are used for identification and isolation of DNA and RNA.
Which one of the following palindromic base sequences in DNA can be easily cut at about the middle by some particular restriction enzyme?
A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Restriction enzymes recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA. Many of them are palindromic, meaning the base sequence reads the same backwards and forwards. Recognition sequences in DNA differ for each restriction enzyme, producing differences in the length, sequence and strand orientation (5' end or the 3' end) of a sticky-end of an enzyme restriction. If we cut the DNA with EcoR1, the DNA would be cut right in the middle. All the pieces would be the same size, which would be 15 kb long.
Option C Hence 5' GAATTC 3' ; 3' CTTAAG 5' palindrome sequence can be easily cut at about the middle by EcoR1 enzyme.
Which one of the following is used as vector for cloning genes into higher organisms?
Retrovirus as has the ability to transform normal cells into cancerous cells. Hence, it can used as a vector for cloning desirable genes into animal cells.
Select the correct statement from the following?
Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. During the process, the primary effluent is taken to aeration tank that contain large number of aerobic heterotrophic microbes. They form flocs that digest a lot of organic matter. As the biological oxygen demand of waste water is reduced, it is passed into settling tank to undergo sedimentation. The sediment of the settling tank is called activated sludge that is a rich source of aerobic bacteria. Hence, the statement
(d) is correct.
Biogas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. It is made up of methane, carbon dioxide with traces of nitrogen, hydrogen sulphide and hydrogen.
Methanobacterium is an anaerobic bacterium that is found in rumen of cattle and is helpful in the breakdown of cellulose.
Polyethylene glycol method is used for
Direct gene transfer is the transfer of naked. DNA into plant cells but the presence of rigid plant cell wall acts as a barrier to uptake. Therefore protoplasts are the favoured target for direct gene transfer. Polyethylene glycol mediated DNA uptake is a direct gene transfer method that utilizes the interaction between polyethylene glycol, naked DNA, salts and the protoplast membrane to effect transport of the DNA into the cytoplasm.
The linking of antibiotic resistance gene with the plasmid vector became possible with
The linking of antibiotic resistance gene with the plasmid vector became possible with DNA ligase. DNA ligase is an enzyme that is able to join together two portions of DNA and therefore plays an important role in DNA repair. DNA ligase is also used in recombinant DNA technology as it ensures that the foreign DNA is bound to the plasmid into which it is incorporated.
Gel electrophoresis is used for
Gel electrophoresis is a technique to separation of DNA fragments according to their size. DNA is negatively charged so in gel tank when electric passed, DNA move towards positive electrode.
Introduction of food plants developed by genetic engineering is not desirable because
Plants developed by genetic engineering are called transgenic plants or genetically modified crops from which genetically modified food is produced. For their production micro-organisms (bacteria, virus) are used. So, by consuming them there is a danger of entry of viruses and toxins causing differ types of allergies and other health hazards to human beings.