Answer : (d)

Answer : (d)

DNA polymerase is isolated from a bacterium, Thermus aquaticus. Specific Bt toxin genes were isolated from Bacillus thuringiensis. 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. The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants. 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. Answer:(d)

restriction enzymes are ‘molecular scissors’–characteristics are as follows 1) Cleaves DNA at specific restriction sites. 2) Can be palindromic 3) Every place there is restriction site on the DAN, it will cleave the DNA 4) Different restriction enzymes will have different DNA sequences for restriction sites 5) Restriction enzymes can be used over and over again 6) Where the DNA cuts, it cam result in blunt ends or staggered cuts with sticky ends Option (b) statement is not correct as it states "cuts only one strand" Answer:(b)

In recombinant DNA technology bacteria is able to produce human insulin because genetic code is nearly universal. Answer:(c)

Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment. Answer:(b)

Some ethical standards are required to evaluate the morality of all human activities that might help or harm living organisms. The Indian Government has set up organisations such as GEAC (Genetic Engineering Approval Committee), which will make decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services. Answer:(d)

The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides. RNAi takes place in all eukaryotic organisms as a method of cellular defense. PCR is now routinely used to detect HIV in suspected AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. Answer:(c)

Selectable markers are those genes which help in selecting those host cells which contain vectors (i.e., transformants) and eliminating the non- transformants. pBR322 is a well characterized plasmid cloning vector containing two antibiotic resistance genes, ampicillin (Amp) and tetracycline (Tet), and several convenient restriction endonuclease sites including EcoRI (RI) and BamHI (Bam). Recombinant DNA technology is the joining together of DNA molecules from two different species. The recombined DNA molecule is inserted into a host organism to produce new genetic combinations Answer:(a)

A wide range of cell types can be microinjected, but we typically use large adherent cells. Adherent cells, also called anchorage-dependent cells, are grown in cell culture medium while attached to the bottom of a tissue culture flask.Statement (I) not correct Allelic (An allele is a variant form of a gene.) sequence variation has traditionally been described as a DNA polymorphism if more than one variant (allele) at a locus occurs in human population with a frequency greater than 0.01 . Statement (iii) is not correct Answer:(d)

In an agarose gel electrophoresis, shortest pieces of DNA will be close to the positive end of the gel i.e., away from the wells, while the longest pieces of DNA will remain near the wells. Answer:(c)

Western blotting is a laboratory technique used to detect a specific protein in a blood or tissue sample. The method involves using gel electrophoresis to separate the sample's proteins. The separated proteins are transferred out of the gel to the surface of a membrane. Answer:(b)

In PCR technique, DNA polymerase is isolated from a bacterium Thermus aquaticus, which remain active during the high temperature induced denaturation of double stranded DNA. Answer:(b)

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. (i) is correct. It was found that Hind II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II. (ii) is correct. 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). (iii) is correct. Origin of replication (ori) : This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. (iv) is correct. DNA is negatively charged because of the presence of phosphate groups in nucleotides. (v) is incorrect. Answer:(b)

Selection of recombinants due to inactivation of antibiotics is a cumbersome procedure because it requires simultaneous plating on two plates having different antibiotics. Therefore, alternative selectable markers have been developed which differentiate recombinants from non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, a recombinant DNA is inserted within the coding sequence of an enzyme, β-galactosidase. This results into inactivation of the gene for synthesis of this enzyme, which is referred to as insertional inactivation. Answer:(a)

DNA polymerase (isolated from a bacterium, Thermus aquaticus), which remain active during the high temperature induced denaturation of double stranded DNA. Answer:(a)

Bacteria protect their DNA by modifying their own recognition sequences, usually by adding methyl (CH3) molecules to nucleotides in the recognition sequences and then relying on the restriction enzymes' capacity to recognize and cleave only unmethylated recognition sequences. Answer:(a)

In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin. Answer:(d)

In order to force a bacterium to take up the plasmid, the bacterial cells have to be made competent. This is done by treating them with a specific concentration of divalent cations such as calcium which increases the efficiency with which the DNA molecule enters the bacteria through pores in its cell wall. Recombinant DNA is then forced into such cells by incubating the cells with recombinant DNA on ice followed by placing them immediately at heat shock and then again into ice. This enables the bacteria to take up the recombinant DNA. Answer:(a)

The techniques of genetic engineering which include creation of recombinant DNA, use of gene cloning and gene transfer, overcome this limitation and allows us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into the target organism. Answer:(d)

Thermus aquaticus is a species of bacterium that can tolerate high temperatures, one of several thermophilic bacteria that belong to the Deinococcota phylum. Answer:(c)

DNA polymerases are widely used for DNA manipulation in vitro, including DNA cloning, sequencing, labeling, mutagenesis, and other purposes. DNA polymerase is an essential component for PCR due to its key role in synthesizing new DNA strands. Answer:(b)

Cellular totipotency is the inherent potentiality of a plant cell to give rise to a whole plant, a capacity that is retained even after a cell has undergone final differentiation in the plant body. Answer:(c)

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

EcoRI is an endonuclease enzyme isolated from strains of E. coli, and is part of the restriction modification system. SalI is a restriction endonuclease used for molecular biology methods to cleave DNA at the recognition sequence 5′-G/TCGAC-3′, generating fragments with 5′-cohesive ends BamH I is a type II restriction endonuclease, having the capacity for recognizing short sequences of DNA. Answer:(a)

More than 400 restriction enzymes have been isolated from the bacteria that manufacture them Answer:(b)

Restriction enzymes belong to a larger class of enzymes called nucleases. They are of two types: Exonuclease They remove nucleotides from the ends of DNA. Endonuclease Endonucleases are enzymes that produce internal cuts called cleavage in DNA molecules. Endonucleases cleave DNA molecules at random sites. A class of endonucleases cleaves DNA only within or near those sites with specific base sequences. These are called restriction endonucleases. Sites recognized by them called recognition sites. (These sites differ for different restriction enzymes). Answer:(c)

Isolation of DNA → Restriction enzyme digestion → Ligation → Transformation Answer:(c)

Transcription factors are proteins that help turn specific genes "on" or "off" by binding to nearby DNA. Operator genes contain the code necessary to begin the process of transcribing the DNA message of one or more structural genes into mRNA. Answer:(c)

Radio active andibody	substance that can be used to identify colonies of genetically engineered bacteria that makes particular gene product
Artificial gene	substance that can be constructed in the laboratory
Amplification	The production of multiple copies of a sequence of DNA. Abnormal enhanced replication of a plasmid many copies of plasmid in each cell
To produce clones	process of producing individual organisms with identical or virtually identical DNA A large population of identical cells
shotgun cloning	A method to generate the templates needed for DNA sequencing. The use of entire array of genes of an organism

Answer:(a)

Plasmids are used in the techniques and research of genetic engineering and gene therapy by gene transfer to bacterial cells or to cells of superior organisms. Assertion is true. Virulence plasmids help bacteria infect humans, animals, or even plants, by a variety of mechanisms. Reason is true but not correct explanation of assertion. Answer:(b)

Calcitonin injection is used to treat Paget's disease of bone, or high levels of calcium in the blood (hypercalcemia). Calcitonin injection is also used to treat osteoporosis in postmenopausal women. Answer:(b)

Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides Answer:(d)

DNA fingerprinting is a laboratory technique used to establish a link between biological evidence and a suspect in a criminal investigation. A DNA sample taken from a crime scene is compared with a DNA sample from a suspect. If the two DNA profiles are a match, then the evidence came from that suspect. Answer:(d)

Answer:(d)

The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants. Answer:(b)

In the eight-cell stage, cells are separated and cultured until small embryos are formed which are implanted into the womb of other cows. This process is known as an artificial twinning method. Answer:(c)

The YAC vector itself provides the essential elements for propagation of DNA as a chromosome in the yeast Saccharomyces cerevisiae. These elements include a yeast centromere, two functional telomeres, and auxotrophic markers for selection of the YAC in an appropriate yeast host. Answer:(b)

A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. The Southern blot is a method for hybridizing one or more labeled DNA probes to a large number of DNA fragments and discriminating among them. The procedure depends on the ability of denatured DNA single strands to bind tightly to nitrocellulose under certain conditions. Answer:(a)

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. 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 (Agarose gel). The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves. Answer:(b)

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. 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 (Agarose gel) 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. Answer:(c)

When cut by the same restriction enzyme, the resultant DNA fragments have the same kind of ‘sticky-ends’ and, these can be joined together (end-to-end) using DNA ligases. (i) is incorrect. Exonucleases remove nucleotides from the ends of the DNA. (ii) is incorrect. The first restriction endonuclease–Hind II. (iii) is correct. Plasmids and bacteriophages have the ability to replicate within bacterial cells independent of the control of chromosomal DNA. (iv) is correct. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning. (v) is incorrect. Answer:(c)

Almost all (99.9 per cent) nucleotide bases are exactly the same in all people. (i) is correct. The average gene consists of 3000 bases, not 30000. (ii) is wrong. Holandric genes are genes situated in the nonhomologous region of the Y chromosome. Chromosome 1 has most genes (2968), and the Y has the fewest (231). (iii) is correct. Less than 2 per cent of the genome codes for proteins. (iv) is wrong. Answer:(c)

Gene-specific probes are produced from specific mRNA by the enzyme reverse transcriptase, which synthesizes a complementary DNA copy (cDNA) from mRNA. If radioactive bases are added to the reaction mixture, the cDNA will be labelled and can thus be used as a hybridization probe to look for the complementary sequences. Answer:(c)

Answer:(b)

A gene may represent only a millionth of the cell's DNA. It's necessary so that a specific region of a genome can be isolated. Answer:(b)

If there are two fragments then fragments can be ligated at one site. This is called restriction site. The two students who have two fragments have one restriction site in this region. Answer:(b)

The International Human Genome Sequencing Consortium published the first draft of the human genome in the journal Nature in February 2001 with the sequence of the entire genome's three billion base pairs some 90 percent complete. Answer:(d)

Restriction endonucleases present in bacteria provide a defence mechanism against invading viruses. Inside the bacterial cell, these enzymes selectively cut up foreign DNA. Answer:(b)

Transgenic mice are being used to test the safety of the polio vaccine. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre. Transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s. Answer:(d)