For the good of progeny: Human Cloning
Cloning of human genes for the good of the progeny Cloning of genes, a process by which a gene can be isolated from all the different genes that exist in an organism, which allows its characterization to be carried out. Molecular cloning is the basis of most genetic engineering procedures and its basic strategy is to move the desired gene from a large and complex genome to a small and simple one.
Molecular cloning can be divided into several steps. First, the deoxyribonucleic acid (DNA) from which it starts should be isolated. If it is genomic DNA, it must be previously digested with restriction enzymes to obtain a mixture of fragments of adequate size for cloning. Reverse transcription synthesized DNA (copyed DNA or cDNA) can also be cloned from the messenger RNA population from a cell, or even DNA synthesized by polymerase chain reaction (CPR).
The second step is to attach the DNA fragments to a cloning vector with the enzyme DNA ligase. The cloning vectors used are plasmids or bacteriophages (viruses capable of infecting bacteria). Cosmids are other artificially constructed cloning vectors that have characteristics of both. Subsequently, these DNA constructions must be introduced and maintained in a host organism, usually a bacterium. Once all these steps are done, a battery of bacteria is obtained that contains all the genes present in an organism.
When digested or fragmented with restriction enzymes, each bacteria contains a fragment of the original genome. This battery of bacteria is called a genomic library. If the cDNA obtained from the total of the messenger RNAs of a cell, each bacteria will contain a single copy of cDNA and, therefore, a single gene, with the advantage that in this case the non-coding information (introns) present in the DNA has been eliminated. Before proceeding to the study of the genes, it is necessary to identify the bacteria that contain the gene or genes of interest. First, those bacteria that have received the cloning vectors from those that did not receive the constructions must be identified.
When the cloning vector is a plasmid, a vector marker (generally resistance to an antibiotic) is normally used, so that only bacteria containing the plasmid can grow in the medium containing said antibiotic. In the case, on the contrary, that the cells contain a phage, it is enough to look for the presence of lysis plates. Second, the bacteria that present the genes of interest must be identified to separate them from the rest. To do this, various strategies are used, ranging from hybridization with nucleic acid probes (both in genomic libraries and in expression libraries), to the use of immunodetection techniques for expression libraries, which allow the detection of the protein produced by the desired gene by specific antibodies. Then, this bacteria is taken and grown to produce a clone of identical bacteria. Since the vector containing the inserted DNA is replicated whenever the bacterial cell divides, a sufficient amount of cloned inserted DNA necessary to characterize the gene is produced.
In this way, it is possible to study the genes that encode proteins and that have a special interest, or those whose inactivation, as a result of a mutation, causes a specific disease. For example, its sequence and the nature of the mutation that gives rise to a disease can be determined. In some cases, the gene can be expressed in the bacterial cell to produce the specific protein (from an expression library), which can be used in the treatment of diseases such as diabetes mellitus (insulin) or dwarfism (growth hormone). Recently, cloned functional genes have been introduced in individuals to treat a disease more directly. It is likely that the use of these genetic treatment procedures with cloned DNA will increase in the future.
** Genetic engineering within the reach of science
** Genetic engineering, a set of techniques that allow modifying the characteristics of an organism in a predetermined sense by altering its genetic material. It is a very broad term that ranges from mutagenesis to artificial selection for the improvement of animals or plants. Genetic engineering is usually used to get certain microorganisms, such as bacteria or viruses, to increase the synthesis of compounds, form new compounds, or adapt to different media, as well as to obtain transgenic animals and plants, or Knockout animals (also called KO) that have certain inactivated genes, which allows verifying the effect that said inactivation exerts on the metabolism.
Another application of this technique, also called a recombinant DNA technique, includes gene therapy, the contribution of a functional gene to a person suffering from a genetic anomaly. Genetic engineering consists of the manipulation of deoxyribonucleic acid (DNA). In this process, the so-called restriction enzymes produced by various bacterial species are very important. Restriction enzymes are capable of recognizing a given sequence of the chain of chemical units (nucleotide bases) that form the DNA molecule, and break it at said location. The DNA fragments thus obtained can be joined using other enzymes called ligases. Therefore, restriction enzymes and ligases allow you to break and reunite the DNA fragments.
Also important in the manipulation of DNA are the so-called vectors, parts of DNA that can self-replicate (generate copies of themselves) regardless of the DNA of the host cell where they grow. These vectors, usually plasmids or viruses, allow you to obtain multiple copies of a specific DNA fragment, which makes them a useful resource to produce sufficient amounts of material to work with. The process of introducing a DNA fragment into a vector is called cloning, since multiple copies of a specific DNA fragment are produced. Another way to get many identical copies of a given part of DNA is the polymerase chain reaction. This method is fast and prevents the preparation of DNA libraries (DNA clones).
** Gene therapy **
Gene therapy consists of the contribution of a functional gene to cells that lack this function, in order to correct a genetic alteration or acquired disease. Gene therapy is divided into two categories. The first is the alteration of the germ cells, that is, sperm or eggs, which causes a permanent change in the entire body and subsequent generations. This germline gene therapy is not considered in humans for ethical reasons.
The second type of gene therapy, somatic cell therapy, is similar to an organ transplant. In this case, one or more specific tissues are subjected, through direct treatment or removal of the tissue, from the addition of a gene or therapeutic genes in the laboratory, together with the replacement of the cells treated in the patient. Various clinical trials of somatic cellular gene therapy for the treatment of cancers or blood, hepatic, or pulmonary diseases have been initiated.
