Question

Chemical mediated gene transfer can be facilitated by

Answer 1

(1) DNA Transfer in Protoplasts

(2) Free DNA Transfer to Intact Tissue

(3) Agrobacterium Mediated Gene Transfer Method

(4) Integration and Expression.

The first transgenic plant was produced via Agrobacterium mediated modified transformation of Nicotiana tabacum protoplasts by Horsch and co-workers in 1984. Since then several dozen plant species have been genetically engineered using different techniques.

Simultaneous development of other techniques such as selectable markers facilitated the development in genetic engineering for obtaining transformed plants. But this technique is not suitable for monocotyledon plants as they are not natural host of Agrobacterium (There is evidence that limited gene transfer is possible in monocots by this system).

Therefore, other methods of direct gene transfer have been developed for use with monocots and other species. These can be categorized on the basis of the use of protoplasts or cell and tissue as the target materials. Freshly isolated protoplasts are used for genetic transformation. Protoplast stage is for a short duration, before it regenerates cell wall, and DNA transfer is performed during this period.

I. DNA Transfer in Protoplasts:

(i) Electroporation

(ii) Chemically stimulated DNA uptake by protoplasts

(iii) Liposomes

(iv) Micro-injection

(v) Sonication

II. DNA Transfer in Plant Tissues:

(i) Acceleration of DNA coated micro-particles

(ii) Laser micro-beam

(iii) Silicon carbide fibres

Direct uptake of DNA by isolated protoplasts is a genotype dependent response. Regeneration from protoplasts is not common in all the species. Due to this, production of fertile transgenic plants has remained difficult in most of the cereal species. However, transgenic fertile plants have been produced in Sorghum vulgare, Oryza sativa and Hordeum vulgare. Direct delivery of free DNA molecules into plant protoplasts by physical (electroporation and micro injection) and chemical (polyethylene glycol) methods have been developed to facilitate DNA delivery across the plasma membrane.

Answer 2

Chemical mediated gene transfer can be facilitated by usage of certain "chemicals such as Polyethylene Glycol".  

Explanation:

The vector less gene transfer includes the following the four important methods,

• Electroportaion: It is the method in which temporary holes are made in plasma membrane which helps in entry of the foreign DNA.

• Chemical mediated gene transfer: It is accomplished by usage of polyethylene glycol which helps in intake of foreign DNA by the cell.

• Micro injection

• Particle gun