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The organism which is used for gene transfer in higher organisms is
A) Agrobacterium tumefaciens
B) E.coli
C) Acetobacter aceti
D) Bacillus thuringiensis

Answer
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Hint:The process in which the genetic materials are transferred from unicellular organisms to other unicellular or multicellular organisms is known as Horizontal gene transfer (HGT) or lateral gene transfer (LGT). In the evolution of many organisms, horizontal gene transfer plays a vital role.

Complete answer:
The genetic material can be transferred from parents to offspring i.e., vertical gene transfer and can be transferred between the organisms i.e., horizontal gene transfer. Agrobacterium tumefaciens is a gram negative rod-shaped soil bacteria. It is found as a pathogen in several dicot plants.

It has the ability to transfer a small piece of DNA known as ‘T-DNA’ that is responsible for the transformation of a normal plant cell into a tumor cell and also direct these cells to induce the chemicals to fulfil the requirement of the pathogen. At the site of wound, the bacterium conquers the plant, transforming them and the adjacent cells to form a tumor known as crown gall.

Additional information:
Escherichia coli is a gram negative rod shaped bacteria that generally lives in the intestines of the warm blooded organisms. Most of them help to maintain the healthy digestive tract and are harmless. Sometimes by consuming the contaminated food and water, some of the strains may cause diarrhea.

Acetobacter aceti: it is a type of gram negative bacteria that uses its peritrichous flagella for locomotion. It is responsible for the conversion of ethanol to acetic acid and was first proved by Louis Pasteur.
Bacillus thuringiensis: it is a gram positive, naturally occurring soil borne bacteria. It is used as a natural biological pesticide as it contains toxic spores.

Therefore the correct answer is option (A) Agrobacterium tumefaciens.

Note:
Apart from Agrobacterium, other ways to transfer foreign DNA into cells are
i) Viral transduction:- It is a method of horizontal gene transfer where the virus is used as a vector for gene transfer.
ii) Transfection:- It is a process in which the DNA is transferred into eukaryotic cells by various chemical and physical methods.
iii) Injection:- It is a common method of gene transfer in which the DNA is injected into the plants physically with the help of gene gun.