The 19th and 20th centuries were marked by great scientific and technological developments. These developments encompassed many different fields like transportation, communication, manufacturing, education, trade, health care and others. Though, by far the most prominent development underlies within the field of science. Nowadays, with the many abilities and capable manipulation methods within a further refined state, human manipulation has become far more apparent, not only as a priority in the field of science, but ultimately within society too. Human manipulation, or colloquially referred to as ‘Genetic Manipulation’ is in essence, a process done to manipulate the genome of an organism in order to produce desired traits. There are two main types of human manipulation that are often more successful than others, these are ; Selective Breeding and Transgenesis, which will be primal focuses throughout this report in addition to the biological implications in which they give forth.
‘Selective Breeding’ and or, ‘Artificial Breeding’, is often referred to as one of the earliest forms of biotechnology and is responsible for many of the plants and animals that we know today. Obligated by Charles Darwin in his widely known work on evolution, Darwin who was, and still remains as one of the greatest biologist minds known to mankind was also considered one of the greatest novelists with his publication of the famous ‘On the Origin of Species’. Though credited, selective breeding itself predates Darwin himself by thousands of years as both plant and animal breeding have been common practice since the birth of civilization. Selective breeding consists of a procedure in which humans intentionally chooses a specific trait they desire from an organism in order to nurture on to an offspring. In order to execute the following, two members of the same species that consists of the particular/desired trait are to be paired as breeding partners in order to encourage and yield desirable characteristics in the offspring. These characteristics tend to lean towards beneficial phenotypic traits such as the following ; tastier fruits and vegetables, crops with greater resistance to pests, and larger animals that can be used for meat. Reasonings behind this stands as although breeding with two of the same species that consists of the desired traits, in fact, does not ensure the likelihood of the offspring inheriting the desired trait. Though it does definitely increase the probabilities in doing so as an organism’s characteristics are partly determined by the combination of gene variants that ensue and passed on from one generation to the next. To infer, with the rise in stocks and economic opportunities within society, it is no surprise that various methods for selective breeding exist, from high-tech and costly processes such as in-vitro fertilisation ; ( the process of fertilization by extracting eggs, retrieving a sperm sample, and then manually combining an egg and sperm in a laboratory dish.) or genetic engineering to more simple low-cost techniques that rely on the selection and controlled mating of animals based on observable characteristics. Ideally, the incentive of selective breeding typically aims to adapt an organism’s characteristics in a way that is desirable to the humans that breed them, which controversially nourishes beliefs whether the ethics of manipulating the genome of an organism is moralistic in it’s doings.
On the contrary, Transgenesis, in which is another form of genetic modification that is far more modernized and complex in comparison to that of selective breeding, involves the the advent of technology which can also be referred to as ‘Transfection’, a term defined as the process in which naked or purified nucleic acids are
deliberately introduced into eukaryotic cells. In simpler terms, transgenesis introduces an ‘Exogenous Gene’ ; ( Exogenous genes refers to any DNA that originates from outside of the organism.) also referred to as a ‘Transgene’ involves the transfer of desired isolated genes, gene fragments, individual chromosomes/ chromosomal fragments, or isolated nuclei that is placed into the genome of an organism in order to allow the organism to exhibit the trait and impart it to the offspring. There are several ways to introduce a transgene into the organism. ‘Microinjection’ is one of the far more popular techniques known. As its name suggests, microinjection is the process of injecting the transgene into the nucleus of a cell where it is randomly inserted into the host genome. In contrast to selective breeding, because Transgenesis requires a more technological base in order to complete, this technique originated and was initiated in 1981, with the purpose commonly interpreted to generate transgenic mice. In essence, in order to complete this process, the target gene in which requires the desired trait must first be identified before being injected and isolated in the nucleus of an organism’s fertilized egg, this stage is interpreted as gene marking. Gene marking is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. In terms of isolating the target gene, ; ( the particular gene being studied or manipulated.) it can usually be isolated simply by breaking up cells mechanically or with chemical treatments such as detergents. In addition, because the isolating gene is disparate from the other cell components, the following can be separated using a technique called ‘Centrifugation’, where the separation process begins by cutting the gene from the rest of the DNA by using a restriction enzyme. Furthermore, after the phase of centrifugation, the fragments would then be separated according to size using a technique called ‘Gel Electrophoresis’ ; ( Gel electrophoresis is a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size.) prior to the preparation of amplifying/copying the gene to make a sufficient quantity using the ‘Polymerase Chain Reaction’ (PCR) where the amplifying occurs, constructing the bases for the final stage where the insertion of the genetic material rounds out the process.
Ultimately, in a comparative lens with the contrast of both Selective Breeding and Transgenesis, the process of selective breeding has been viewed as tedious and time-consuming and especially with the increasing market pressures to produce animals, which grow faster, yield more milk, lay bigger eggs and so on. It is not surprising that with how transgenesis has developed alongside the advancements of technology, the approach that combines breeding with molecular genetics and recombinant DNA technology, has given better results within a short span of time, doesn’t seem all bad.
EX 1: Cows
Selective breeding of animals has undermined enormous production gains and farming efficiencies in dairy and the consumptions of meat. Case in point, cows exemplify the following with unprecedented relations. In terms of originated information, cows have been domesticated as early as 9000 BC. Breeders continue to employ artificial selection to this day, compounding with improved productivity and thus profits. With regards to cows, breeders whom are often dairy farmers or just simply farmers alone will look for the cows that can either produce the most
milk or inherit a greater muscle mass and ultimately only breed those cow in hopes for ; Increased milk production and udder size ; Increased size and muscle mass or an overall increase in fat and protein content (Desirable Traits). An example of this can be seen with the ‘Belgian Blue’. The belgian blue, also referred to as ‘Beef Cattles’ originates in central and upper Belgium where they consist of a natural mutation within the ‘Myostatin Gene’ ; (muscle cell growth and differentiation) which codes for protein. In addition, because myostatin is a protein that inhibits muscle development and interferes with fat deposition, hence why the reasonings behind their great mass, resulting in very lean meat and an accelerated rate of growth due to the myostatin gene being unable to function at its normal capacity, which is why they are also mentioned as beef cattles, as breeders primarily focus on the possession of meat they present. Ultimately, what this also means is that whether its accounting for an increased size of muscle mass like the belgian blue or an increase of production in milk outtake, over time the quality of the desired traits within a cow will increase as the favoured offspring reproduce repeatedly, meaning that cows will reproduce and the gene pool of the next generation will have a higher frequency of the favoured genes if breeders were to only seek out the cows that already consist of presentable phenotypic features, as alluded above.
Lest we forget, just because breeders opt to breed organisms, such as cows, that may have one or more of the desirable traits in which the breeders are seeking, the results are not always reliable or particularly guaranteed due to hidden genes and mutations that may occur. To further elaborate, just because the phenotype may seem to be advisable, the genotype and therefore phenotype of its offspring may not be suitable. Though as time goes on, the selective breeding process is slowly becoming more and more successful with higher rates of an offspring that concludes the desired traits. With how time and science have developed alongside another, methodical ways have presented itself in order to increase the probabilities and odds of receiving the desired trait. One of these methods are determining the genotype of the organism prior to breeding. Hence why with the knowledge, breeders can potentially and intentionally just crossbreed two members of the same species in which possess either both homozygous dominant or homozygous recessive genes and almost guarantee a purebred offspring. This is considered as ‘Test Cross’ ; (a genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the organism.) Another method that cases and consists of a far more efficient pedigree is the marker assisted selection (MAS), which I have mentioned above. MAS is typically used for determining a trait/DNA that is much more difficult to measure compared to others. In terms of the process for MAS, which I have vaguely mentioned, the process begins with identifying or ‘Mapping’ the gene of interest/desired in order to apply the applicable information for the MAS. Then, the markers are implemented and utilised conveniently nearby the gene of interest to ensure that only a minimal portion of the selected individuals will be recombinants.
Although this entirely may seem beneficial for mankind and it presents many advantages, these advantages do overshadow the disadvantages, but they do not go unscathed. The more and more selective breeding, not just for cows, but overall, will decrease the size of the gene pool, losing the variety of life. Though looking in from an outsider’s perspective these implications that come along with the process of selective breeding do seem as if the good outweighs the bad meaning that more humans will get to eat and survive with a greater rate of products being inherited.
Similar to cows and within the concept of selective breeding, another example is underlined when it comes to dogs. It is no surprise that there is an estimate of over 400 breeds of dog in the world and all are maintained as pure-bred stocks through selective breeding, which aims to maintain a closed genetic lineage. Just like cows, though in a lesser manner, when an interesting or useful trait is identified in a dog, owners would breed from that dog in the hope of the trait being passed on. Over many rounds of such breeding attempts, especially where two dogs with the same trait are to bred with each other, traits became fixed. Meaning that If you understand the genetics, you can predict what you can see in a crossbreed. In terms of processes, the process in which is bestowed upon selective breeding for the cows can also be accounted for that of the dogs, though interpreted in a concept. As upon dogs, breeders do not seek masculinity and or dairy production but instead seek the desirable traits in which assists behavioural control. These behavioural control typically leans towards learning tricks and being capable of learning commands. Just like the cows, when the desired traits are identified and accounted for, the breeder will obligate two dogs to breed with one another in order to create an offspring. Though, because the process is the same, success rates are not ensured despite whether the desired traits are apparent within one of the parents, of even both.
In the case of implications, health and or survival of the organisms are typically at risk through the process of breeding. Other traits get carried along with the blocks of genetic material on a chromosome housing a gene for a particular trait. Many of which are not wanted or even desirable. Hence many dogs also develop unusual diseases (many of which look very similar to human diseases). Many develop disease including heart disease, cataracts, cancers, deafness and hip dysplasia. This is because genetic mutations that cause these have also been carried along or fixed into these breeds through continual selective breeding.
With the amount of selectively bred cows, as a race, it was only a matter of time until the implementation of transgenesis was also bestowed upon cows themselves. The first transgenic cow was produced in 1997. It is a relatively new technology in comparison to selective breeding, as alluded to, but several transgenic breeds have since been developed. Ultimately, cows are an attractive target for the concept of transgenesis because they naturally secrete large quantities of protein in their milk. This means that, if done correctly, the protein encoded by a transgene will be expressed in the cows milk and can easily be isolated. Thus proteins of therapeutic benefits for humans could be produced in large quantities, relatively inexpensively.
In the case of the process in which is needed to advert a transgenic cow, a multi step procedure is required. Scientists who produce transgenic cows use an array of techniques which include the likes of ; Restriction enzymes, DNA cloning, PCR, Vitro Embryo production and many more.. The process of transgenesis begins with an identification phase in which the an analysis must be made in order to find the desirable trait wanted in the transgenic organism. The desired gene sequence is then extracted from the source organism’s DNA which is obtained from a genomic library, where a plethora of cloned segments of DNA is stored while containing at least one copy of every DNA from a particular organism. After the gene has been located and identified, the DNA must be removed with, as alluded to before, a restriction enzyme which enables the DNA to be cut causing the pieces to be sequential in various lengths. After the isolating phase, the transgene is then made by modifying the gene itself.