All Free Biology MCQs with Answers

• A. Azotobacter
• B. Rhizobium of the roots of leguminous plants
• C. Agrobacterium
• D. Yeast as a 2 mm plasmid

Explanation: Ti plasmid (tumor inducing) from the soil bacterium Agrobacterium tumefaciens is effectively used as a vector for gene transfer to plant cells. The part of Ti plasmid transferred into plant cell DNA is called the T-­DNA. This T­-DNA with desired DNA spliced into it is inserted into the chromosomes of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random. Such plant cells are then cultured, induced to multiply and differentiate to form plantlets. Transferred into the soil, the plantlets grow into mature plants, carrying the foreign gene, expressed throughout the new plant.

• A. Alkaline phosphatase
• B. Catalase
• C. DNA probe
• D. RNAase.

Explanation: ELISA (enzyme linked immunosorbent assay) screening test is the initial test to diagnose AIDS. The test works by detecting antibodies/ substances or protein which are produced in the blood when the virus is present.Alkaline phosphatase and peroxidases are commonly used enzymes as key reagents to perform the ELISA test. These enzymes are used to provide antibody-­antigen complex in a specialized ELISA plate or tray. In ELISA test for detecting a particular antigen, its antibody is buffered and a drop of serum (supernatant of centrifuged blood) is poured over it. If the latter contains antigen, it will produceantigen­ antibody complex. A second enzyme labelled antibody is added. It forms an enzyme­antigen­ antibody complex if the antigen is present. The substrate is now added. It produces a stain if the antigen is present.

• A. Hydrolytic enzyme
• B. Powerful antibiotic
• C. Human insulin
• D. Isoenzyme.

Explanation: Human insulin (humulin) is the first therapeutic product produced by means of recombinant technology by Eli Lilly and Co. on July 5, 1983.

• A. Tobacco
• B. Cotton
• C. Pea
• D. Flax

Explanation: Transgenic plants are those plants in which a foreign gene has been introduced and stably integrated into host DNA. The first transgenic plants were produced in tobacco (Nicotiana tabacum). A gene resistant to PPT (L­-phosphinothricin), an active ingredient of herbicide 'Basta', was isolated from Medicago sativa. It inhibits the enzyme GS (glutamine synthase) which is involved in ammonia assimilation. This gene resistant to PPT was incorporated into tobacco, as a result of which transgenic tobacco was produced which was resistant to PPT.

• A. Foreign DNA in all its cells
• B. Foreign DNA in some of its cells
• C. Foreign DNA and RNA in all its cells
• D. Foreign DNA and RNA in some of its cells

Explanation: A transgenic organism is one that has become transformed following the introduction of novel genes into its genome. It is most frequently achieved by the integration of cloned DNA sequences following their injection into the fertilized egg. This fertilized egg divides mitotically to form the whole organism so that all the cells of the organism will carry the transferred gene. The transferred genes are known as transgenes. Transgenesis can be done by pronuclear microinjection and somatic cell nuclear transfer or cloning. Transgenic animals produced by this technology include mice, Drosophila, Xenopus and some of the fish species.

• A. Acetocarmin
• B. Aniline blue
• C. Ethidium bromide
• D. Bromophenol blue

Explanation: The separated DNA fragments can be seen only after staining them with a compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange coloured bands.

• A. Vector
• B. Plasmid
• C. Structural gene
• D. Selectable marker

Explanation: Some genes called "selectable markers" help in selecting those host cells which contain the vectors (transformants) and eliminating the non­transformants.

• A. The smaller the fragment size, the farther it moves
• B. Positively charged fragments move to farther end
• C. Negatively charged fragments do not move
• D. The larger the fragment size, the farther it moves

Explanation: Electrophoresis is a technique used for the separation of substances of different ionic properties. Since the DNA fragments are negatively charged molecules, they can be separated by allowing them to move towards the anode. DNA fragments move towards the anode according to their molecule's size through the pores of agarose gel. Thus, the smaller fragments move farther away as compared to larger fragments.

• A. Downstream processing
• B. Bioprocessing
• C. Post-production processing
• D. Upstream processing.

Explanation: After the formation of the product in the bioreactor, it undergoes some processes before a finished product is ready for marketing. The process includes separation and purification of products which is collectively called downstream processing.

• A. Purification of product
• B. Addition of preservatives to the product
• C. Availability of oxygen throughout the process
• D. Ensuring anaerobic conditions in the culture vessel

Explanation: A stirred­-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor.