Answer : (d)

The cutting of DNA by restriction endonucleases results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. 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 can see bright orange coloured bands of DNA in a ethidium bromide stained gel exposed to UV light (Figure). Answer : (d)

Bioreactor is an apparatus for growing organisms (yeast, bacteria, or animal cells) under controlled conditions. Used in industrial processes to produce enzymes, pharmaceuticals, vaccines, or antibodies Answer : (d)

During the isolation of desired gene, chilled ethanol is used for the precipitation of DNA. Chilled alcohol increases the yield of DNA. Answer : (b)

Golden rice is vitamin A enriched rice, with a gene from daffodil and is rich in carotene. Answer : (b)

retroviruses have been disarmed and are now used to deliver desirable genes into animal cells. Answer : (c)

PCR is based on three simple steps required for any DNA synthesis reaction: (1) denaturation of the template into single strands (2) annealing of primers to each original strand for new strand synthesis and (3) extension of the new DNA strands from the primers. Answer : (d)

There is a definite region in E. coli DNA where the replication originates. Such regions are termed as origin of replication. It is because of the requirement of the origin of replication that a piece of DNA if needed to be propagated during recombinant DNA procedures, requires a vector. The vectors provide the origin of replication. Answer : (d)

Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA. Polymerases are enzymes that catalyze the synthesis of DNA or RNA polymers whose sequence is complementary to the original template, Answer : (c)

Insulin is composed of two peptide chains referred to as the A chain and B chain. A and B chains are linked together by two disulfide bonds, and an additional disulfide is formed within the A chain. In most species, the A chain consists of 21 amino acids and the B chain of 30 amino acids. Insulin molecules have a tendency to form dimers in solution due to hydrogen-bonding between the C-termini of B chains. Additionally, in the presence of zinc ions, insulin dimers associate into hexamers. Answer : (a)

In recombinant DNA technology, human genes are often transferred into bacteria or yeast because both bacteria and yeast multiply very fast to form huge population, which express the desired gene. Answer : (a)

A genetic preservation is the first step in the cloning process, allowing you to produce an identical genetic twin or clone, which will be born at a later place in time. Answer : (b)

Most ELISA methods developed for the detection of antigen or antibody consist of use of corresponding antibody or antigen in question which is firmly fixed on solid phase, such as plastic surface of polyvinyl plate or polystyrene tube. Such systems are also called Solid Phase Immunosorbent Assay (SPIA). Test sample is added in the microtitre plate, if there is presence of Ag or Ab in the test sample, there will be Ag-Ab reactions (with immobilized Ab or Ag). Later enzyme labelled antibody is added in the reaction mixture, which will combine with either test antigen or Fc portion of test antibody. The enzyme system consists of; An enzyme: horse radish peroxidase, alkaline phosphatase which is labelled or linked, to a specific antibody. A specific substrate: O-Phenyl-diamine-dihydrochloride for peroxidase P Nitrophenyl Phosphate- for Alkaline Phosphatase Substrate is added after the antigen-antibody reaction. The enzyme catalyses (usually hydrolyses) the substrate to give a color end point (yellow compound in case of alkaline phosphatase). The intensity of the color is proportional to the amount of antibody or antigen present in the test sample, which can be quantified using ELISA reader. Answer : (c)

Severe combined immunodeficiency (SCID) is a group of rare disorders caused by mutations in different genes involved in the development and function of infection-fighting immune cells. It is characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations that result in differing clinical presentations. Answer : (b)

Golden Rice is a variety of rice (Oryza sativa) produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of the rice. Answer : (a)

ends of DNA fragments are sticky/It is a short sequence of DNA that is not base paired with other DNA. These sticky ends are helpful for research scientists. If two pieces of DNA are cut with the same restriction enzyme, they would both have the same sticky ends with the same overlaps. When these two pieces of DNA are combined, they have complementary sticky ends, meaning they could base-pair together. Using sticky ends helps scientists ensure the DNA sequences they are working with can be joined together easily. They fit together perfectly, like pieces of a puzzle. The restriction enzyme EcoRI makes sticky ends when it cuts DNA. If both sequences are cut with EcoRI, they can be joined together. Answer : (a)

In 1997, the first transgenic cow, Rosie, produced human alpha-lactalbumin -enriched milk at 2.4 grams per litre statement (a) is not correct Restriction enzymes used in the laboratory to manipulate fragments of DNA, restriction enzymes (or restriction endonucleases) are used to cut DNA into smaller fragments. The cuts are always made at specific nucleotide sequences. Different restriction enzymes recognise and cut different DNA Statement (b) is not correct Answer : (d)

Restriction endonucleases make cuts at specific positions within the DNA. 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. This leaves single stranded portions at the ends. There are overhanging stretches called sticky ends on each strand. Answer : (c)

Monascus purpureus is the yeast used commercially in the production of blood cholesterol-lowering statins. Answer : (d)

Brazzein is a sweet-tasting protein found in the fruit of the native West African Oubli plant (Pentadiplandra brazzeana). It is a soluble protein with a sweetness that is approximately 1500 times greater than sucrose. Protein brazzein and the gene coding, it is patented in the U.S.A. It is proposed to transfer the brazzein gene into maize and express it in maize kernels from where it can be easily extracted Answer : (b)

Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA. Answer : (c)

plasmids and bacteriophages have the ability to replicate within bacterial cells independent of the control of chromosomal DNA. Answer : (a)

Alien DNA is introduced into host cell. Cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun. This method is suitable for plant. Answer : (a)

Agrobacterium tumefaciens. The bacterium causes abnormal growths or galls on roots, twigs, and branches of euonymus and other shrubs primarily in the rose family. The bacterium stimulates the rapid growth of plant cells that results in the galls. Answer : (b)

Alpha-1 antitrypsin deficiency-associated lung disease is characterized by progressive degenerative and destructive changes in the lungs (emphysema, commonly of the panacinar type). Emphysema is a chronic, usually slowly progressive illness, which most commonly causes shortness of breath. Alpha-1 antitrypsin is used to treat emphysema. Answer : (d)

small ringlets of DNA called plasmids float about freely in the cytoplasm of certain bacterial cells and replicate independently from the coding strand of DNA. These plasmid DNA act as vectors to transfer the piece of DNA attached to it. Answer : (d)

Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer. Answer : (c)

Answer : (c)

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA. The transgenic plant therefore got itself protected from the parasite. Answer : (b)

A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA. Answer : (a)

Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer. Answer : (a)

Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Transgenic animals can be specifically designed to allow the study of how genes are regulated, and how they affect the normal functions of the body and its development, e.g., study of complex factors involved in growth such as insulin-like growth factor. By introducing genes from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body. Answer : (d)

DNA vaccines are third generation vaccines. A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen (such as a bacterial surface protein) that stimulates an immune response into bacterial or mammalian cells, expressing the antigen in these cells and then purifying it from them. Answer : (c)

Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). Dolly is the first sheep which was made by cloning technique. Bt brinjal is inserted with a new gene for cry proteins. This protein which is produced helps to protect the crop plant from the infestation by boll worm. The golden rice is introduced with a gene which produces pro-vitamin A. Tracy is the modified sheep produced by genetic engineering. The sheep is capable to produce the human protein alpha antitrypsin, in her milk. Answer : (a)

Reverse transcriptase (RT), also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into DNA. This enzyme is able to synthesize a double helix DNA once the RNA has been reverse transcribed in a first step into a single-strand DNA. Answer : (b)

Plasmid DNA act as vectors to transfer the piece of DNA attached to it. Plasmids have the ability to replicate within bacterial cells independent of the control of chromosomal DNA. Answer : (c)

In the medical laboratory PCR can be used to screen for genetic disorders and to identify cancers and pathogens. Clearly PCR is enormously important for both the scientist and the non-scientist alike. The technique was developed by Kary Mullis in the 1980s, and he received the 1993 Nobel Prize in chemistry as a result. Answer : (b)

Bt Cotton: Some strains of Bacillus thuringiensis produce proteins crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. The Bt toxin protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect Answer : (a)

Bt toxin is produced by a bacterium called Bacillus thuringiensis. Answer : (c)

The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance. Answer : (c)

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals. Transgenic animals are useful: (i) Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated, and how they affect the normal functions of the body and its development. (ii) Study of disease (iii) Biological products (iv) Vaccine safety (v) Chemical safety testing Answer : (d)

Small ringlets of DNA called plasmids float about freely in the cytoplasm of certain bacterial cells and replicate independently from the coding strand of DNA. They have their own replication origin site, a selectable marker, and a restriction or cloning site. Answer : (a)

Restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. In bacterial cell, restriction enzymes cleave foreign DNA, thus eliminating infecting organisms. Answer : (c)

Answer : (c)

The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance. Answer : (a)

RNA interference (RNAi) takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Answer : (b)

Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt corn Answer : (c)

Transgenic organisms can be produced by incorporating the desired gene into the genome of the organism. For this purpose, the gene of interest is introduced into the nucleus of the germ cell of the organism. Answer : (b)

Small ringlets of DNA called plasmids float about freely in the cytoplasm of certain bacterial cells and replicate independently from the coding strand of DNA. Extra chromosomal DNA used as vector in gene cloning is plasmid. Answer : (d)

Restriction nucleases is also known as molecular scissors as they cut any DNA fragment at specific position. Restriction endonucleases make cuts at specific positions within the DNA. Answer : (b)