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Genetic Engineering

Marker Assisted Selection

What is marker-assisted selection (MAS)?
"Natural selection" refers to survival of the fittest. Farmers often selectively breed crops (or animals) for desirable traits, however – in this case it’s they and not nature who make the selection. To do this, they need to first grow the plants (animals) to maturity. Genetic markers offer a way to do the same thing much faster when the traits can be identified with markers which are either the genes themselves or DNA which is very closely linked.

What goals can be achieved through the use of MAS?
Marker assisted selection can make use of the diversity which exists within a plant species, and also with those closely related species which can naturally hybridize with it. Because the genetic code can be read before the plant is full grown, the "selection" phase can be considerably shortened. This process does not involve genetic engineering (gene splicing). Since multiple crossings are usually needed to develop a new plant line, the time saving – a genetic test which takes hours and can be performed on a single cell substituting for a growing season – is very significant.

Just as no two people are alike, there is diversity (variability) in the genetic makeup of plants. This genetic diversity can be mobilized effectively by MAS. Many new varieties (soy beans with altered linolenic acid content, rice with higher iron content for instance) have been developed in this way. Drought resistance, insect resistance and other traits which exist in some individuals within a species can be selectively enhanced.

Marker assisted selection versus genetic engineering
When organisms are produced using genetic engineering, new organisms are produced by a process involving the insertion of a package of DNA into cells or embryos. In agriculture, the goal of genetic engineering was to produce new varieties containing one or more desired traits taken from unrelated species. The insertion of the novel genes has been unpredictable and the possibility genes landing in the wrong places, in multiple copies, or infliction of genetic damage has been significant. The use of viral promoters and antibiotic resistance genes as part of the process has introduced further risks. The chance the novel genetic code will be unstable and cause problems in future seasons also exists. Transgenes such as Bt or herbicide resistance are often expressed in every cell of the plant and all season long which may exert a yield drag.

Organisms produced using MAS have reproduced in conventional ways. Each gene in their genome is derived from either its male or female parent. These organisms contain neither the DNA for anti-biotic resistance nor the viral DNA that is often used to promote the expression of the genes for the desired traits. Random insertions and fragmentary insertions are not a problem. This makes MAS safer than genetic engineering. Indeed, it is just as safe as conventional plant breeding by farmers. Another advantage is that MAS varieties will not cause problems for organic farmers.


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