The 7 branches of Genetics (and what each one studies)
The genetic, the area of study of biology that seeks to understand the biological inheritance encoded in DNA, has given us essential answers to almost all the processes that surround us. From the evolution of living beings to congenital diseases, everything is related in one way or another to our genome.
The premise is simple: every cell in a diploid organism has a nucleus, with DNA organized in the form of chromosomes. Of the total chromosomes (46 in humans), 23 come from the mother and 23 from the father (22 autosomal pairs, one sexual). Thus, we have two copies of each chromosome and, therefore, of each gene. Each of these alternative forms of the gene is called an "allele", and it can be dominant (A), recessive (a) or codominant.
The information encoded in genes undergoes a process of transcription and translation, and nuclear DNA gives rise to a strand of messenger RNA, which travels to the cytoplasm. This RNA has the information necessary for protein synthesis by ribosomes, responsible for assembling proteins through a specific order of amino acids. Thus, the genotype (genes) is transformed into the phenotype (tissues and characters made up of proteins). With all these terms in mind, we present to you the 7 branches of genetics. Do not miss it.
What are the main disciplines within Genetics?
When studying the world of genes, the first contact always comes in the form of Mendel's studies and the distribution of characteristics in peas over the generations. This is what we know as "classical genetics" or "Mendelian genetics", but in no case does it encompass the entire discipline. Stay with us, as we now dissect each of the branches of this fascinating field of science.
1. Classical genetics
As we have said, classical genetics is one that describes character inheritance very simply. It has been vitally useful in laying the foundations of genetics in the past, but the truth is that fewer and fewer traits are being discovered to be eminently Mendelian. For example, eye color is encoded by at least 4 genes, so the classical allele distribution cannot be applied to calculate the iris color of children.
Mendel's laws, however, explain the basis for many congenital diseases that are monogenic (encoded by a single gene). These applications can be defined briefly:
- Principle of uniformity: when two different homozygous individuals are brought together (AA dominant and aa recessive), all the children will be heterozygous (Aa) without exception.
- Segregation principle: When 2 heterozygotes are crossed, the proportions are 1/4 homozygous dominant (AA), 2/4 heterozygous (Aa) and 1/4 homozygous recessive (aa). By dominance, 3/4 of the offspring have the same phenotype.
- Independent transmission principle: there are traits that can be inherited independently from others, if their genes are on different chromosomes or in regions that are very distant from each other.
Mendel's laws explain some features of the phenotype of the individual based on their alleles, but there is no doubt that the interaction between genes and the environment affects the final product.
2. Population genetics
Population genetics is responsible for studying how alleles are distributed in a population of a given species in nature. It may sound like anecdotal knowledge, but it is necessary to estimate the long-term viability of a population and consequently begin planning conservation programs before disaster strikes.
Broadly speaking, it is established that the higher the percentage of homozygotes for different genes in a population, the more it is at risk of disappearing. Heterozygosity (2 different alleles for the gene) reports some variability and greater adaptive capacity, so a high index of heterozygosity usually indicates a healthy population status. On the other hand, homozygosity suggests reproduction among few individuals, inbreeding and lack of adaptation.
3. Molecular genetics
This branch of genetics studies the function and conformation of genes at the molecular level, that is, on a “micro” scale. Thanks to this discipline, we have at our disposal advanced techniques for the amplification of genetic material, such as PCR (polymerase chain reaction).
This tool makes it possible, for example, to obtain a sample of the mucosa of a patient and efficiently search for the DNA of a virus or bacteria in the tissue environment. From the diagnosis of diseases to the detection of living beings in an ecosystem without seeing them, molecular genetics makes it possible to obtain vital information only with the study of DNA and RNA.
4. Genetic engineering
One of the most controversial branches of genetics, but also the most necessary. Unfortunately, the human being has grown at the population level beyond his possibilities, and nature often does not provide the rhythm that is required to maintain the rights of all the members of the planet. Genetic engineering, among many other things, has the objective of contribute beneficial traits to the crop genome so that production is not diminished by environmental impositions.
This is achieved, for example, by genetically modifying a virus and causing it to infect the cells of the target organism. If done correctly, the virus will die after infection, but it will have successfully integrated the genetic section of interest into the DNA of the species, which is now considered transgenic. Thanks to these mechanisms, nutritious superfoods and crops resistant to certain pests and climatic stressors have been obtained. And no, these foods do not cause cancer.
5. Developmental genetics
This branch of genetics is responsible for studying how a whole organism appears from a fertilized cell. In other words, investigates gene expression and inhibition patterns, the migration of cells between tissues and the specialization of cell lines according to their genetic profile.
6. Quantitative genetics
As we have said before, very few features or characters of the phenotype can be explained in a purely Mendelian way, that is, with a single dominant (A) or recessive (a) allele. Monogenic traits are counted: a famous example within this category that serves to exemplify classical Mendelian inheritance is albinism and its pattern of inheritance, but at the normal trait level it is somewhat unusual.
Quantitative genetics deals with explain the variation of phenotypic traits in much more complex characters to explain, how the color of the eyes, skin and many other things. In other words, it studies polygenic characters that cannot be understood only by the distribution of a pair of alleles of a single gene.
Genomics is perhaps the most booming branch of genetics, since the first step to develop all the fronts of this general discipline is know how many genes a species has in its cells, where they are found and the sequence of nucleotides that make them up. Without this information, it is impossible to carry out work on genetic engineering, population genetics or developmental genetics, since not knowing which are the essential loci within a chromosome makes it impossible to draw conclusions.
Thanks to branches such as genomics, the human genome has been sequenced and we know that we have about 25,000 genes, with 70% of total DNA of the extragenic type and the remaining 30% of material related to genes. The challenge, today, is to elucidate what work has all that DNA not present in the genes on the development of the phenotype. This is the work of epigenetics, but due to its distance from the matter that concerns us, we will explain it in another moment.
As you may have seen, the branches of genetics touch all the sticks of human life: the genome of living beings conditions agricultural production, the permanence of species in ecosystems, fetal development, the inheritance of congenital diseases and any biological process that occurs to you. Like it or not, we are our genes and mutations, and many deaths are explained based on all these premises. Without going any further, cancer is nothing more than a mutation in a cell line, right?
With all these lines we wanted to exemplify that, as ethereal as the study of genes sounds, it has infinite utilities at the level of production, health and conservation. Let us not stop claiming the need to recognize the world's geneticists and employ those who cannot practice their profession, since the answer to all vital processes is found in the genome.