BY-B . S C ( H ) B I O T E C H N O L O G Y

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TRANSGENIC FOOD AND POULTRY

INTRODUCTION TO TRANSGENIC FOOD

• Transgenic food is also known as genetically modified food.

• Genetically engineered foods have had foreign genes (genes from other plants or animals) inserted into their genetic codes.

• The inserted gene sequence (transgene) may come from another unrelated plant, or completely different species.

• Genetic engineering speeds up the process and increase the variety of genes which can be inserted into a particular plant.

HISTORY

Was under trial and error for almost 9900 years.

The first genetically modified plant was produced in 1962’ using an antibiotic- resistant tobacco plant.

The first genetically modified crop approved for sale in the U.S., in 1994, was the FlavrSavr tomato, which had a longer shelf life, as it took longer to soften after ripening.

As of mid- 1996, a total of 35 approvals had been granted to commercially grow 8 transgenic crops and one flower crop of carnations, with 8 different traits in 6 countries plus the EU. In 2000, with the production of golden rice, scientists genetically modifies food to increase its nutrient value for the first time.

TRANSGENIC FOODS IN THE WORLD

A lot of foods has been altered and made genetically modified. These are-

o Cotton o Riceo Soybeano Sugar Caneo Tomatoeso Sweet corno Canola o Potatoo Papayao Sugar beet

WHO’S ON THE TOP ?

HOW TO MAKE TRANSGENIC PLANTS

In order to make a transgenic crop, there are five main steps:1. Extracting DNA2. Cloning a gene of interest3. Gene for plant infiltration4. Transformation5. Plant breeding

EXTRACTING DNA:DNA is first extracted from cells and put into a bacterial plasmid. Plasmid is a molecular biological tool that allows any segment of DNA inbe put into a carrier cell (usually a bacterial cell) and replicatedproduce more of it.

CLONING A GENE OF INTEREST:A bacterial cell (i.e. E. coli) that contain a plasmid can put aside and used over &over again to produce copies of the gene the researcher is interested in, a

processthat is generally referred to as “cloning” the gene. 

GENE FOR PLANT INFILTERATION:Once the gene of interest has been amplified, it is time to introduce it into plant species we are interested in. The nucleus of the plant cell is the target for the new transgenic DNA.There are many methods of doing this but the two most common methods includethe “Gene Gun” and “Agro bacterium method”.

The “Gene Gun” method, also known as the micro-projectile bombardmentmethod, is most commonly used in species such as corn and rice. As its nameimplies, this procedure involves high velocity micro-projectiles to deliver DNAinto living cells using a gun. It involves sticking DNA to small micro-projectilesand then firing these into a cell. This technique is clean and safe. It enablesscientists to transform organized tissue of plant species and has a universaldelivery system common to many tissue types from many different species. It cangive rise to un-wanted side effects, such as the gene of interest being rearrangedupon entry or the target cell sustaining damage upon bombardment.Nevertheless, it has been quite useful for getting trans genes into organisms when no

otheroptions are available.

The Agrobacterium method involves the use of a soil- dwelling bacteriaknown as Agrobacterium tumefaciens, which has the ability to infect

plantcells with a piece of its DNA. The piece of DNA that infects a plant isintegrated into a plants chromosome through a tumor-inducing plasmid(Ti plasmid), which can take control of the plant’s cellular machinery anduse it to make many copies of its own bacterial DNA. The Ti plasmid is alarge circular DNA particle that replicates independently of the bacterialchromosome.

Transfer DNA on a plasmid in Agrobacterium

The importance of this plasmid is that it contains regions of transfer DNA (tDNA), where a researcher can insert a gene, which can be transferred to a plant cell through a process known as a floral dip. A floral dip involves dipping flowering plants into a solution of Agrobacterium carrying the gene of interest, followed by the transgenic seeds being collected directly from the plant. This process is useful in that it is a natural method of transfer and therefore thought of as a more acceptable technique. In addition, Agrobacterium is capable of transferring large fragments of DNA very efficiently without substantial rearrangements, followed by maintaining high stability of the gene that was transferred [1]. One of the biggest limitations of Agrobacterium is that not all important food crops can be infected by this bacteria.

TRANSFORMATION:Transformation is the heritable change in a cell or organism broughtabout by the uptake and establishment of introduced DNA. 

PLANT BREEDING:Plants are grown under controlled environmental conditions in a series ofmedia containing nutrients and hormones, a process known as tissueculture. Once whole plants are generated and produce seed, evaluation ofthe progeny begins. This regeneration step has been a stumbling block in producing transgenic plants in many species, but specific varieties of most crops can now be transformed and regenerated.

Tissue culture of transgenic plants in a controlled environmental chamber. Source: USDA

Leaf disc method for A.t mediated transformation

TYPES OF GENETIC ENGINEERING

TRANSGENIC PLANTS: Have genes inserted into them that are derived from another species. The inserted genes can come from species within the same kingdom ( plant to plant) or between kingdoms ( for example, bacteria to plant). Transgenic carrots have been used to produce the drug Taliglucerase alfa which is used to treat Gaucher’s disease.

CISGENIC PLANTS: Are made using genes found within the same species or a closely related one, where conventional plant breeding can occur.

SUBGENIC PLANTS: In 2014, Chinese researcher Gao Ciaxia filed patents on the creations of a strain of wheat that is resistant to powdery mildew. The strain lacks genes that encode proteins that repress defenses against the mildew. The researchers deleted all three copies of the genes from wheat’s hexaploid genome. The strain promises to reduce or eliminate the heavy use of fungicides to control the disease.

GM FOOD CLASSIFICATION

IGeneration

•Crops have enhanced input traits, such as herbicide tolerance, better insect resistance, and better tolerance to environmental stress.

II Generation

• Crops include those with added-value output traits, such as nutrient enhancement for animal feed.

IIIGeneration

• Crops include those that produce pharmaceuticals, improve the processing of bio-based fuels, or produce products beyond food and fiber (Fernandez-Cornejo and Caswell 2006).