BIOLOGY 1.5 Marks Questions

→ In addition to 'ori', the vector requires a selectable marker.
→ It helps in identifying and eliminating non transformants and selectively permitting the growth of the transformants.
→ Transformation is a procedure through which a piece of DNA is introduced in a host bacterium,
→ Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli.
→ The normal E. coli cells do not carry resistance against any of these antibiotics.

→ Reporter enzymes are used to identify transformants which which is active. contains receptor gene
→ For example; beta galactosidase (lac z) activity can not be seen in transformant cell so, they appear white in colour whereas non transformants gives blue colour colonies.
→ This shows that in non transformant cell there is no foreign gene inserted.

In the DNA palindromic sequence is complimentary and opposite to each other.
(1) 5'..... GGATCC.....3'
3'..... CCTAGG..... 5'
(2) 5'..... AAGCTT.....3'
3'.....TTCGAA.....5"
(3) 5'.....ACGCGT.....3'
3'.....TGCGCA.....5'
(4) 5'.....ACTAGT.....3'
3'.....TGATCA.....5'
(5) 5'.....AGGCCT.....3'
3'.....TCCGGA.....5'

→ No, eukaryotic cells do not have restriction endonucleases, because, the DNA of eukaryotic cell is strongly methylated by methylase enzyme.
→ Restriction endonucleases enzymes are present in prokaryotic cell which protects DNA from the adverse effect of Virus.

→ Enzymes are smaller in size than DNA molecules.
→ We know this because DNA contains genetic information for the development and functioning of all living organisms.
→ It contains instructions for the synthesis of proteins and DNA molecules.
→ Enzymes are proteins which are synthesised from a small stretch of DNA known as 'genes',
→ which are involved in the production of the polypeptide chain.

→ Exonucleases: Exonucleases cut the DNA from the ends where it breaks the sugar phosphate bond of nucleotides.
→ Endonucleases: Endonucleases cut the DNA at specific site where it breaks sugar phosphate bonds as well as produce sticky ends.

→ Chitinase is an enzyme.
→ It is used in the DNA isolation from fungi where it breaks down the glycosidic bonds present in fungal cellwall.

→ Origin of replication is a specific genome sequence, from where replication is originated.
→ When any gene or segment of DNA linked with this Ori, unable the replication of that gene in the host cell.
→ This sequence is responsible to maintain copies of linked DNA.
→ If we want high number of clones then we have to select the vector in a such way which favours the gene to produce high number of copies.

→ It is less expensive.
→ Oxygen availability is high throughout the bioreactor.
→ Having good fermentation capacity.
→ Products are produced on a large scale.

→ Recombinant DNA technology involves several steps in specific sequence such as
(1) Isolation of DNA, fragmentation of DNA, isolation of a desired DNA fragment.
(2) ligation of the DNA fragment into a vector and formation of recombinant DNA.
(3) Transferring the recombinant DNA into the host cell.
(4) Culturing the host cells and selection of clones.
(5) Expression of genes in host cell and obtaining the gene product.

→ After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it is ready for marketing as a finished product.
→ The processes include separation and purification, which are collectively referred to as downstream processing.
→ The product has to be formulated with suitable preservatives.
→ Such formulation has to undergo through clinical trials as in case of drugs.
→ Strict quality control testing for each product is also required.
→ The downstream processing and quality control testing vary from product to product.

→ Plasmid is an extra small circular DNA present in the bacterium cell which is different from other DNA.
→ Plasmid is able to replicate independent of the chromosomal DNA in the cell.
→ It contains genes which can produce specific type of chemicals.
→ Plasmid can be extracted from the cell.
→ The specific sequence of plasmid can be cut by using restricted endonucleases and at that place desirable gene can be introduced by ligase enzyme.
→ Plasmid plays significant role in recombinant DNA Technology.

→ Since DNA is a hydrophilic molecule, it cannot pass through cell membranes.
→ In order to force bacteria to take up the plasmid, the bacterial cells must first be made 'competent' to take up DNA.
→ This is done by treating them with a specific concentration of a divalent cation, such as calcium, which increases the efficiency with which DNA enters the bacterium through pores in its cell wall.
→ Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42°C (heat shock).
→ Finally, putting them back on ice.
→ This enables the bacteria to take up the recombinant DNA.
→ Due to heat and cold effect the pore size of cell membrane is manipulated.

→ Mostly plasmid and bacteriophage is used as a cloning vector.
→ Plasmid and bacteriophage have the potential to replicate independently in the host cell without having control of chromosomal DNA.
→ In each cell there are plenty of copies of bacteriophage which contains many copies of their genome.
→ In certain bacteria, there are one or two copies of plasmid.
→ Whereas others may have 15-100 copies per cell. Their numbers can go even higher.
→ If we are able to link an alien piece of DNA with bacteriophage or plasmid DNA, we can multiply its numbers equal to the copy number of the plasmid or bacteriophage.
→ Vectors used at present, are engineered in such a way that they help easy linking of foreign DNA and selection of recombinants from non- recombinants.wm

→ Among many, the two core techniques that enabled birth of modern biotechnology are:
(1) Genetic engineering :
→ Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism.
(2) Bioprocess engineering :
→ Maintenance of sterile (microbial contamination- free) ambience in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc.

→ T-DNA is a gene of Agrobacterium tumifaciens bacterium.
→ Agrobacterium tumifaciens, a pathogen of several dicot plants.
→ The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens is able to deliver a piece of DNA known as 'T-DNA' to transform normal plant cells into a tumor.
→ These tumor cells produce the chemicals required by the pathogen.
→ The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector, which is no more pathogenic to the plants.
→ Ti plasmid is still able to use the mechanisms to deliver genes of our interest into a variety of plants.

→ Traditional hybridisation procedures used in plant and animal breeding, very often lead to inclusion and multiplication of undesirable genes along with the desired genes.
→ The techniques of genetic engineering which include creation of recombinant DNA(r-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.