The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution.[1][2] In 1978 Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."[3][4]
The dark-coloured or melanic form of the peppered moth (var. carbonaria) was not known before 1811. After field collection in 1848 from Manchester, an industrial city in England, the frequency of the variety was found to have increased drastically. By the end of the 19th century it almost completely outnumbered the original light-coloured type (var. typica), with a record of 98% in 1895.[5] The evolutionary importance of the moth was only speculated upon during Darwin's lifetime. It was 14 years after Darwin's death, in 1896, that J.W. Tutt presented it as a case of natural selection.[6] Due to this, the idea widely spread, and more people believed in Darwin's theory.
Bernard Kettlewell was the first to investigate the evolutionary mechanism behind peppered moth adaptation, between 1953 and 1956. He found that a light-coloured body was an effective camouflage in a clean environment, such as in Dorset, while the dark colour was beneficial in a polluted environment like in Birmingham. This selective survival was due to birds which easily caught dark moths on clean trees, and white moths on trees darkened with soot. The story, supported by Kettlewell's experiment, became the canonical example of Darwinian evolution and evidence for natural selection used in standard textbooks.[7]
However, failure to replicate the experiment and criticism of Kettlewell's methods by Theodore David Sargent in the late 1960s led to general skepticism. When Judith Hooper's Of Moths and Men was published in 2002, Kettlewell's story was more sternly attacked, accused of fraud, and became widely disregarded. The criticism became a major argument for creationists. Michael Majerus was the principal defender. His seven-year experiment beginning in 2001, the most elaborate of its kind in population biology, the results of which were published posthumously in 2012, vindicated Kettlewell's work in great detail. This restored peppered moth evolution as "the most direct evidence", and "one of the clearest and most easily understood examples of Darwinian evolution in action".[8]
Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of an organism's genes using biotechnology. It is a set of technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. New DNA is obtained by either isolating and copying the genetic material of interest using recombinant DNA methods or by artificially synthesising the DNA. A construct is usually created and used to insert this DNA into the host organism. The first recombinant DNA molecule was made by Paul Berg in 1972 by combining DNA from the monkey virus SV40 with the lambda virus. As well as inserting genes, the process can be used to remove, or "knock out", genes. The new DNA can be inserted randomly, or targeted to a specific part of the genome.
An organism that is generated through genetic engineering is considered to be genetically modified (GM) and the resulting entity is a genetically modified organism (GMO). The first GMO was a bacterium generated by Herbert Boyer and Stanley Cohen in 1973. Rudolf Jaenisch created the first GM animal when he inserted foreign DNA into a mouse in 1974. The first company to focus on genetic engineering, Genentech, was founded in 1976 and started the production of human proteins. Genetically engineered human insulin was produced in 1978 and insulin-producing bacteria were commercialised in 1982. Genetically modified food has been sold since 1994, with the release of the Flavr Savr tomato. The Flavr Savr was engineered to have a longer shelf life, but most current GM crops are modified to increase resistance to insects and herbicides. GloFish, the first GMO designed as a pet, was sold in the United States in December 2003. In 2016 salmon modified with a growth hormone were sold.
Genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. In research GMOs are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. By knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. As well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. The same techniques that are used to produce drugs can also have industrial applications such as producing enzymes for laundry detergent, cheeses and other products.
The rise of commercialised genetically modified crops has provided economic benefit to farmers in many different countries, but has also been the source of most of the controversy surrounding the technology. This has been present since its early use; the first field trials were destroyed by anti-GM activists. Although there is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, GM food safety is a leading concern with critics. Gene flow, impact on non-target organisms, control of the food supply and intellectual property rights have also been raised as potential issues. These concerns have led to the development of a regulatory framework, which started in 1975. It has led to an international treaty, the Cartagena Protocol on Biosafety, that was adopted in 2000. Individual countries have developed their own regulatory systems regarding GMOs, with the most marked differences occurring between the US and Europe.
Darwinian of Carbon
Gene therapy (also called human gene transfer) is a medical field which focuses on the utilization of the therapeutic delivery of nucleic acids into a patient's cells as a drug to treat disease.[1][2] The first attempt at modifying human DNA was performed in 1980 by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989.[3] The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990. It is thought to be able to cure many genetic disorders or treat them over time.
Gene therapy using an adenovirus vector. In some cases, the adenovirus will insert the new gene into a cell. If the treatment is successful, the new gene will make a functional protein to treat a disease.
Between 1989 and December 2018, over 2,900 clinical trials were conducted, with more than half of them in phase I.[4] As of 2017, Spark Therapeutics' Luxturna (RPE65 mutation-induced blindness) and Novartis' Kymriah (Chimeric antigen receptor T cell therapy) are the FDA's first approved gene therapies to enter the market. Since that time, drugs such as Novartis' Zolgensma and Alnylam's Patisiran have also received FDA approval, in addition to other companies' gene therapy drugs. Most of these approaches utilize adeno-associated viruses (AAVs) and lentiviruses for performing gene insertions, in vivo and ex vivo, respectively. ASO / siRNA approaches such as those conducted by Alnylam and Ionis Pharmaceuticals require non-viral delivery systems, and utilize alternative mechanisms for trafficking to liver cells by way of GalNAc transporters.
The concept of gene therapy is to fix a genetic problem at its source. If, for instance, in an (usually recessively) inherited disease a mutation in a certain gene results in the production of a dysfunctional protein, gene therapy could be used to deliver a copy of this gene that does not contain the deleterious mutation, and thereby produces a functional protein. This strategy is referred to as gene replacement therapy and is employed to treat inherited retinal diseases.[5][6]
While the concept of gene replacement therapy is mostly suitable for recessive diseases, novel strategies have been suggested that are capable of also treating conditions with a dominant pattern of inheritance.
The introduction of CRISPR gene editing has opened new doors for its application and utilization in gene therapy, as instead of pure replacement of a gene, it enables correction of the particular genetic defect.[7] Solutions to medical hurdles, such as the eradication of latent human immunodeficiency virus (HIV) reservoirs and correction of the mutation that causes sickle cell disease, may be available as a therapeutic option in the next couple of years.[8][9][10]
Prosthetic gene therapy aims to enable cells of the body to take over functions they physiologically do not carry out. One example is the so-called vision restoration gene therapy, that aims to restore vision in patients suffering from end-stage retinal diseases.[11][12] In end-stage retinal diseases, the photoreceptors, as the primary light sensitive cells of the retina are irreversibly lost. By the means of prosthetic gene therapy light sensitive proteins are delivered into the remaining cells of the retina, to render them light sensitive and thereby enable them to signal visual information towards the brain. While first clinical trials are ongoing (NCT02556736, NCT03326336 at clinicaltrials.gov), there is still some debate regarding which light sensitive protein should be delivered into which cells.[13]
Not all medical procedures that introduce alterations to a patient's genetic makeup can be considered gene therapy. Bone marrow transplantation and organ transplants in general have been found to introduce foreign DNA into patients.[14] Gene therapy is defined by the precision of the procedure and the intention of direct therapeutic effect.
En Español
The gene is the basic physical unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify traits. Genes are arranged, one after another, on structures called chromosomes. A chromosome contains a single, long DNA molecule, only a portion of which corresponds to a single gene. Humans have approximately 20,000 genes arranged on their chromosomes.
A gene could be as short as a few hundred base pairs or as long as many thousands. The BRCA1 and BRCA2 genes, for instance, are very long and huge. The beta-globin gene, on the other hand, is only a few hundred of these nucleotides. A gene, in a common way of thinking about it, is a packet of information coding generally for a protein. Of course, [in] DNA, the gene doesn't do the work. It's the protein that's produced from that that carries out the function. It's gotten [a] little messy in that one gene doesn't just make one protein. Oftentimes, because of alternative splicing, one gene can produce multiple proteins. And of course there are genes that don't even make proteins at all. They make RNAs that have some other functional role. And some people have begun to question whether the term "gene" is useful because it's gotten so complicated. Not to worry, it is still a very useful term. Geneticists wouldn't know how to have a conversation without using the word.
Deoxyribonucleic acid (DNA) is the chemical information database that carries the complete set of instructions for the cell as to the nature of the proteins produced by it, its life span, maturity, function and death. Genes are the working subunits of DNA. Each gene contains a particular set of instructions, usually coding for a particular protein or for a particular function.