Biotechnology and its Applications Test - 20

Induction of cell suspensions or callus tissue to differentiate into embryo is known as somatic embryogenesis.  The resultant embryoids are not from the fusion of two germ cells and hence can not develop into transgenic plants. Fusion of protoplasts from similar or contrasting cell types to somatic hybrids is process known as protoplast fusion. Pectinase break up cell aggregates into individual cells and the cellulase digests cell wall to get protoplast suspensions. It is then centrifuged, washed in medium without the enzyme, and separated from intact cells and cell debris by rotation on a cushion of sucrose. Protoplasts synthesize new cell walls within 510 days on nutrient medium followed by cell division. But this technique has not been successfully implemented till date. Transgenic plants are produced by introduction of foreign DNA, that carries the gene for desired traits, into the individual's DNA using r-DNA techniques to get a new species carrying traits which were not there in it. 

RNA synthetase is also known as RNA replicase which catalyzes RNA synthesis in virus-infected host cells. Restriction endonucleases recognize specific sequences in the DNA and cut the DNA into fragments. The nif genes encode enzymes involved in the fixation of atmospheric nitrogen into a form of nitrogen which is available to living organisms. H. G. Khorana and co-workers synthesized the gene for E. coli tyrosine tRNA precursor. The tyrosine tRNA precursor has 126 nucleotides. A complete sequence of dsDNA coding for tyrosine tRNA precursor of E. coli was synthesized. He then synthesized biologically functional gene coding for tyrosine t-RNA of E.coil. It was 207 base pairs long with 51 bp long promoter region, a 126 bp long precursor region of tRNA, a 25 bp long DNA in which 16 base pairs contained the restriction site for Eco RI. Option D is the correct answer.

Correction option: D

Explanation for correction option:  

• Gene therapy is the process of the introduction of DNA into living human beings in order to treat disease.
• It is used to replace a missing gene product or to correct mutant alleles.
• The first human gene therapy trial was conducted at the National Institutes of Health in Bethesda, Maryland, in 1990 on a four-year-old girl suffering from ADA deficiency (Adenosine deaminase deficiency).
  A functional ADA gene was introduced 
• A functional ADA gene was introduced ex vivo into the bone marrow cells of the child through an engineered retrovirus containing a functional ADA gene. The treated cells were reintroduced into the patient’s marrow.

Transgenesis is the process of insertion of a foreign gene into the genome of selected organism to improve its quality. The first transgenic experiments in mammals were performed in mice. Most of the transgenic experiments are still carried out with mice and hence they exists in maximum number.

Rice produces carotene in the leaves but the biosynthetic pathway is turned off during plant development in grains. Transgenic rice, golden rice, were engineered by inserting two genes that restart the carotenoid biosynthetic pathway leading to the production and accumulation of carotene in the grains. These are the naturally occurring down-regulated genes. But the transgenic variety does not show down-regulation. Further, the presence of cry gene confers resistance to certain pests and insects. Therefore, the crop gives high yield while sustaining the aroma. Thus, the correct answer is D.

Gene cloning is the process of making the copies of gene of interest by locating it in DNA followed by extraction of DNA containing that gene. A probe is a radiolabeled single-stranded DNA/ RNA fragment used to search for a gene of interest or other DNA sequence. For the purpose, the base sequence of probe is complementary to the target sequence to facilitate its base pairing with target gene. Gene multiplication is a mechanism that increase the genes in their number of copies. It is also called as gene amplification and is the source of evolution. Gene therapy is the process of introduction of DNA into living human beings in order to treat disease. It is used to replace a missing gene product or to correct mutant alleles. Correct answer is C.

• Biopiracy is the illegal use of certain products which have an origin in some other area. Biopiracy is performed by obtaining patents for those products and having benefits without making the original region knowing about the same. 
• Biopiracy can be done with respect to research work going on in some other part of the world. The same organism or process can be used to obtain money and benefit. 
• Traditional knowledge about medicines or certain medicinal herbs can be exploited to obtain royalty through patents. Certain products like chemicals, biomolecules, drugs, and genes may already be discovered by a certain group. The right may be obtained against these products or these may be produced or sold to obtain money.

Gene therapy can be used to add the external DNA to the genome to replace a missing gene product, gene targeting to correct mutant alleles or to treat dominantly acting diseases via antisense RNA expression or the expression of intracellular antibodies. If the mutated gene makes a faulty protein or no protein, gene therapy introduces a normal copy of the gene, via a vector, to restore the function of the gene to produce a functional protein. 

Humulin is the genetically engineered insulin produced by inserting human insulin gene into a host cell (E. coli) which was then allowed to grow and reproduce normally. The inserted human DNA lead them to produce a synthetic version of human insulin. Hybrid is a offspring of two genetically dissimilar animals or plants which carries genetic material from both parents and express new specific genetic characteristics. The dark bluish or brownish pigment obtained by the oxidation of haeme that has contain iron in the ferric state is known as haematin. Hybridomas are the hybrids produced by introducing specific antigen into a mouse to collect antibody-producing cells. These cells are then fused with myeloma cell to produce hybridomas which multiply indefinitely and thus provide infinite source of a specific antibody.