Borlaug developed improved wheat varieties, and the increased use of herbicides also provided incentives to breed for herbicide tolerant crops. In the beginning of the 1970s, cells from two tobacco species were fused and the first somatic hybrid plant was produced. The knowledge about cell functions and gene regulation increased, and with the ability to use restriction enzymes, the cell’s built-in “scissors”, came the ability to cut specific genes out of the DNA. This was one important tool that led to the construction of the first recombinant organisms, including the transgenic bacteria that still provide us with insulin today. In the beginning of the 1980s, researchers managed to create the first transgenic plant, a tobacco plant, with the help of the soil bacterium Agrobacterium tumefaciens. In nature, this bacterium causes plants to grow tumours by inserting its DNA into the plant’s genome, but now those genes could be replaced by any other gene of interest. Not all plant species were susceptible to infection by the bacterium, so other methods were developed such as the gene gun with which the desired DNA could be shot into the plant. Soon genetically modified (GM) plants appeared around the world, first in field trials then as commercial crops. At the same time, AI of sows became routine and methods for embryo transfer were established in dairy cows to enable those with the best breeding values to produce more calves. The first GM animal was a mouse that received
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genes important for growth from a rat, but the application of GM technology for commercial breeing of farm animals has been limited, for ethical and economic reasons. In animal breeding, researchers have focused on estimation of breeding values and the use of gene maps that provide information about the location and arrangement of specific genes on a particular chromosome (see page 28). The gene maps are full of genetic markers that do not themselves govern any particular traits but can be used for selection if they are located close to genes that do affect important traits. Today, selection with the assistance of one or multiple genetic markers is used both in plant and animal breeding. Since the first farm animal (the chicken) had its full genome mapped (i.e., its entire DNA sequence was described), most of the domesticated livestock species have had their genomes mapped. The first steps from the random mutation breeding by radiation or chemicals to precise alterations through site-directed mutagenesis were taken about 40 years ago, but it has only been in recent years that these new methods have been sufficiently refined for use in commercial applications. However, public acceptance of the use of gene technology in agriculture has not been as large as for medical applications.