All Free Biology MCQs with Answers

• A. Radish
• B. Corn
• C. Maize
• D. Carrot
• E. Mango

Explanation: The correct answer is Carrot. F.C Steward was a pioneer in plant tissue culture and used carrot phloem tissue to show that plant cells have the ability to develop into a whole plant, which is a demonstration of cellular totipotency. This was a significant breakthrough in biotechnology, as it laid the groundwork for modern plant tissue culture techniques. Radish, corn, maize, and mango were not used in Steward's experiments, which focused specifically on the carrot.

• A. Under the influence of agar
• B. By diffusion
• C. Under the influence of an electric field
• D. Active transport
• E. By osmosis

Explanation: In gel electrophoresis, molecules migrate through the gel under the influence of an electric field. When an electric current is applied, charged molecules such as DNA, RNA, or proteins move toward the electrode with the opposite charge. The gel acts as a molecular sieve, allowing smaller molecules to move faster than larger ones, thus achieving separation based on size and charge. The incorrect options, such as agar, diffusion, active transport, and osmosis, do not involve the electric field mechanism that is central to gel electrophoresis.

• A. New males
• B. New females
• C. New breeds
• D. New organs

Explanation: Correct. Artificial selection leads to the development of new breeds of plants and animals with improved or specialized characteristics, such as higher milk production in cows or drought resistance in crops.

• A. Rapid growth
• B. Rapid aging
• C. Identical offspring
• D. Absence of mitosis

Explanation: Cloned animals tend to age faster due to shortened telomeres, inherited from the donor cell.

• A. Stem
• B. Root
• C. Flower
• D. Leaf

Explanation: Meloidogyne incognita, commonly known as the root-knot nematode, infects the roots of various plant species, including tobacco. The nematode causes characteristic galls or swellings on the roots, which can lead to stunted growth and reduced crop yield. So, in the case of tobacco plants, it is the roots that are infected by Meloidogyne incognita.

• A. Omega-3
• B. Vitamin A
• C. Vitamin B
• D. Vitamin C

Explanation: Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of B­-carotene (provitamin A - inactive state of vitamin A). B­-carotene is a principal source of vitamin A. The grains of this rice are yellow in color due to B­-carotene and are commonly called golden rice.

• A. Exposing the plants to cold for a brief period
• B. Allowing the plant roots to stand in water
• C. Infection of the plant by Agrobacterium tumefaciens
• D. Altering the pH of the soil and then heat­ shocking the plants.

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 then differentiate to form plantlets. Transferred into the soil, the plantlets grow into mature plants, carrying the foreign gene, expressing throughout the new plant.

• A. Action of gut microorganisms
• B. Presence of conversion factors in the insect gut
• C. Alkaline pH of the insect gut
• D. Acidic pH of the insect gut

Explanation: Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms some protein crystals which contain a toxic insecticidal protein. This toxin does not kill the Bacillus (bacterium) because it exists as inactive protoxins in them. But, once an insect ingests it, it is converted into an active form of toxin due to the alkaline pH of the alimentary canal. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause swelling and lysis and finally cause the death of the insect.

• A. Insects
• B. Herbicides
• C. Fungi
• D. Bacteria

Explanation: Glyphosate is a broad-spectrum herbicide that especially kills broad-leaved herbs. Crop plants may also get affected by the herbicide, thus now crop plants are genetically engineered for glyphosate resistance. So, when glyphosate herbicide is applied, only weeds and no crop plants get harmed.

• A. Insulin
• B. Estrogen
• C. Thyroxin
• D. Progesterone

Explanation: The recombinant DNA technological processes have made a great impact in the area of health care by mass production of safe and more effective therapeutic drugs. In 1983, Eli Lily, an American company, first prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of Escherichia coli to produce insulin chains. Chains A and B were produced separately, extracted, and combined by creating disulfide bonds to form human insulin (humulin).