Biotechnology and its Applications Test - 33

Plants are genetically engineered usually for the appearance of a trait that isn't naturally seen in them. They can be genetically engineered to make them stronger, resistant against pests, less dependant on the use of fertilizer and water, decrease susceptibility to herbicides and for production of all essential amino acids. 

Polymerase Chain Reaction is a method widely used to make many copies of a specific DNA segment. Using PCR, a single (or more) copy of a DNA sequence is exponentially amplified to generate thousands to millions of more copies of that particular DNA segment. Components of PCR include DNA template, DNA polymerase, two DNA primers, nucleotides.

The transgenic food, containing enzyme produced by antibiotic resistance gene, can cause allergies because it is a foreign protein. The bacteria present in alimentary canal can take up antibiotic resistance gene and become resistant to that antibiotic. Transgenes can endanger native species if Bt toxin is expressed in pollens which are transported by pollinator.honeybees. GM crop production causes charges in natural environment which may be harmful for all organisms.

Cry II Ab and cry I Ab produce toxins that are formed by the introduction of Bt genes in plants that helps to prevent them from small pests like cotton bollworms and corn borer.

Meloidogyne incognita infect the roots of tobacco plants and causes a great reduction in yield. Fire and Mello (1998) invented a novel strategy to prevent this infestation. It was based on the process of RNA interference.

A soil-inhabiting plant bacterium Agrobacterium tumefaciens is a pathogen of several dicot plants. It is able to transfer a piece of DNA known as 'T-DNA' into the plant cells. The T-DNA causes tumours, the tumours are called crown galls. Tumour formation is induced by Ti plasmid (Ti for tumour inducing). As gene transfer occurs without human effort, the bacterium is called natural genetic engineer of plants. Similarly retroviruses in animals including humans are able to change normal cells into cancerous cells. So, the correct answer is 'Agrobacterium tumefaciens'.

PCR stands for Polymerase Chain Reaction which is used for amplification of DNA. Rest 3 options are correct as Ti for Tumor inducing, DNA probe identifies the desired DNA fragment and agarose is used as matrix in get electrophoresis.
So, the correct option is option C.

Two cry genes, CrylAc and CryllAb have been incorporated in cotton. The genetically modified crop is called Bt cotton as it contains Bt toxin genes. The genes CrylAc and cryllAb control cotton bollworms.

• During amphimixis, fertilization creates a noncellular cell that includes genetic material from each gamete. 
• In nature, several organisms produce clones through agamogenesis(asexual reproduction).
•  Offspring don't possess actual copies of parental DNA. Hence, the term 'Clone' can't be used for offspring made by amphimixis(sexual reproduction).

• Soil bacterium Bacillus thruingiensis (Bt) produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
• Bacillus thuringinesis forms some intracellular protein crystals. These crystals of Bt toxin contain a toxic insecticidal protein. 
• The Bt toxin protein exists as an inactive toxin and is converted into an active form due to the alkaline pH of the alimentary canal that solubilities the crystals. 
• The activated toxin binds to the surface of midgut epithelial cells and creates pores which cause cell swelling and lysis and finally cause the death of the insect.