Biotechnology Test - 7

Primers are chemically synthesized oligonucleotides that are complementary to the regions of DNA and the enzyme DNA polymerase.

Downstream processing is the separation and purification of recombinant protein product. Downstream processing and quality control testing vary for different products

Gel electrophoresis technique involves separation of different segments of DNA according to their size. The smallest bands in the agarose gel will be towards positively charged anode.

Option (C) is correct answer because a single stranded DNA or RNA tagged with a radioactive molecule is called a probe and it helps in the detection of mutated gene.

Option (A), (B) and (D) are not correct because YAC, BAC, pBR322 are vectors.

If the process of replication ‘of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a thermophilic bacterium Thermits aquaticus), which is active during the high temperature induced denaturation of double stranded DNA.

Option (b) is the correct answer because when restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands, then single stranded portions are left at the ends. These overhanging stretches on each strand are called sticky ends.

Option (1) is the correct answer because separation of DNA fragments which is carried out after restriction enzyme digestion, is done by a technique known as gel electrophoresis.

Option (2) is not the correct answer because polymerase chain reaction (PCR) is a technique used for amplification of gene of interest.

Option (3) is not the correct answer because recombinant DNA technology comprises altering genetic material outside an organism to obtain enhanced and desired characteristics in living organisms or as their products.

Option (4) is not the answer because Southern blotting is a method used for detection of specific DNA sequences in samples.

Option (3) is the correct answer because cellulase is used to isolate genetic material from plant cells and chitinase is used to isolate genetic material from fungal cells.

Option (2) is incorrect because protease is used for digestion of proteins.

Option (1) and (4) are incorrect because lipase is used for the breakdown of lipids.

Both the statements are correct but the given reason is not the correct explanation. Polymerase chain reaction is used in DNA amplification.

Ampicillin resistance gene is a selectable marker that helps to check transformation by selection of transformants.

The correct sequences of process of recombinant DNA technology are Isolation of DNA, fragmentation of DNA by restriction endonuclease, isolation of desired DNA fragment, ligation of DNA fragment into vector, transferring of into host and culturing in host cell to get desired product.

Option (a) is the correct answer because both the statements I and II are correct. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. It will bind to the DNA and cut each of the two strands of double helix at specific points. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome site; but between the same two bases on the opposite strands. So both the statements I and II are correct.

The sequence of the 5 ’and 3 ’primers for the given DNA sequence will be 5 ’AATGC 3 ’, 5 ’GACTC 3 ’.

Option (d) is the correct answer. Cloning vectors are the carriers of the desired gene in the host cell. The features desirable in a cloning vector are :-

• Presence of origin of replication
• Presence of marker genes
• Presence of very few, preferably single recognition site for the commonly used restriction enzymes

The agarose gel with high percentage of agar will lead to accumulation of large sized DNA fragments near the wells as pore size is small near the well.

Various enzymes like protease, RNase, etc. are added to break down substances like proteins, RNA, etc. Once all these substances are broken down, DNA is left which is precipitated out by adding chilled ethanol.

Ethanol has a lower dielectric constant than water, making it to promote ionic bond formation the Na⁺ (from the salt) and the PO⁻₃ (from the DNA backbone), further, causing the DNA to precipitate.