Assertion (A): In recombinant DNA technology, lysozyme is used for disrupting bacterial cells while cellulase is used for plant cells.
Reason (R): Isolation of genetic material needs disruption of cells.
Choose the most appropriate answer from the options given below:
Lysozyme digests bacterial cell walls and cellulase digests plant cell walls. Cell disruption is necessary for DNA isolation, but the reason does not explain why different enzymes are used.
Transformation transfers recombinant DNA into host bacteria. A cloning site contains restriction enzyme recognition sites. Antibiotic resistance genes are selectable markers, and ori is the origin of replication.
Which of the following statements are not true regarding restriction endonucleases?
(A) They are called molecular scissors. (B) These are the enzymes responsible for restricting the growth of bacteriophages in E. coli. (C) They cut the DNA only at the centre of the palindromic sites. (D) They remove nucleotides only from the ends of DNA fragments. (E) They recognise specific palindromic base-pair sequences.
Choose the correct answer from the options given below:
Restriction endonucleases are molecular scissors that recognize specific palindromic sequences. They do not always cut exactly at the centre of the recognition site, and they do not remove nucleotides from DNA ends; that is the function of exonucleases.
Arrange the following steps of DNA fingerprinting in the correct sequence:
(A) Isolation of DNA and its digestion by restriction endonucleases. (B) Hybridisation using a labelled VNTR probe. (C) Transferring of separated DNA fragments to synthetic membranes. (D) Detection of hybridised DNA fragments by autoradiography. (E) Separation of DNA fragments by electrophoresis.
The correct sequence is DNA isolation and digestion → electrophoresis → Southern blotting (transfer) → hybridisation with labelled VNTR probe → autoradiography.
Which of the following statements are correct with respect to DNA separation, isolation and visualization?
(A) The cutting of DNA is done by molecular scissors. (B) The DNA fragments separate according to their size in an agarose gel upon electrophoresis. (C) The separated DNA fragments can be seen without staining when exposed to UV light. (D) The separated DNA fragments, when stained with ethidium bromide, can be seen under UV light.
Choose the correct answer from the options given below:
Restriction endonucleases are molecular scissors. DNA fragments separate by electrophoresis. Ethidium bromide-stained DNA fluoresces under UV light, not without staining.
Insertion of a foreign DNA at BamHI site in an E. coli cloning vector pBR322 results in the loss of antibiotic resistance towards:
The BamHI restriction site lies within the tetracycline resistance gene (tetR) of pBR322. Insertional inactivation results in loss of tetracycline resistance.
