The 8 branches of Genetics (and their characteristics)

Without genetics, explaining life is impossible. All living beings have at least one cell, and for a cell to be such, it must contain genetic material in the form of DNA and be capable of self-replication By itself.

Thanks to the enzymatic activity (DNA polymerase, among others), the substrates (nucleotides) and a standard chain, life is capable of generating one copy or more than one double helix of DNA, and therefore, life new.

With this simple premise, the permanence of living beings on Earth and much more complex things, such as inheritance mechanisms, are explained. Thanks to cell division by meiosis, gametes with half the genetic information of a normal parental cell can be generated, a condition known as haploidy (n). When two haploid gametes unite, a diploid (2n) zygote is generated, containing half the information from the mother and half from the father. This is how, for example, heredity works in our species.

In any case, the deterministic and Mendelian view of genetics is in full challenge. Over the years, the human being has realized that the genome is not restricted only to paternal inheritance, but that there are mutations and environmental variations that can modify the expression of genes throughout life, giving rise to the unusual phenotypic diversity exhibited by species. In the following lines, we will see what they are

the branches of genetics and their characteristics.

• Related article: "Differences between DNA and RNA"

What are the branches of genetics?

Genetics can be defined as a branch of the science (specifically biology) that deals with the study of genes, genetic variation and the mechanisms of inheritance of organisms. The main objective of this discipline is to understand, with the help of biochemical and physiological bases, how it is produced the inheritance of the genotype and phenotype from generation to generation in the different species, with even more attention on the human.

Before going directly into the subject, it is necessary that you have certain clear ideas. As we have said, half of the information in each of our cells comes from the mother, and the other half from the father. In other words, we have a total of 23 pairs of chromosomes, (46 = 23 maternal + 23 paternal). In addition, each chromosome contains coding sequences for proteins or RNA, called "genes."

Since we have two chromosomes of each type (from 1 to 23), we will have two copies of the same gene, one present on the paternal chromosome and one on the maternal chromosome, in a fixed position. Each of the variations that a gene can adopt is known as an “allele”, so we can also affirm that all our genes have two alleles in the genome of the individual, one maternal and the other paternal.

With these data, it only remains to know that a typical allele can be dominant (A) or recessive (a). Thus, for the same gene, an individual can be homozygous dominant (AA), homozygous recessive (aa) or heterozygous (Aa). With these bases in place, let's see what the branches of genetics are.

1. Mendelian genetics or classical genetics

This branch of genetics is one that approaches the study of genes without the use of molecular tools, just as you did Gregor mendel in his day with his experiments with peas over different generations. Briefly, we review Mendel's three laws in this list:

• Principle of uniformity: if two homozygous (AA and aa) are crossed for a gene, all the offspring will be heterozygous (Aa). The trait shown will be the dominant one, that is, the one encoded by the allele (A).
• Segregation principle: if the generation of heterozygotes (Aa) is crossed between them, things change. ¼ of the offspring will be homozygous dominant (AA), ¼ will be homozygous recessive (aa) and 2/4 will be heterozygous (Aa). The dominant character is expressed in 3 out of 4.
• Independent transmission principle: if two genes are sufficiently separated from each other or on two different chromosomes, they can be inherited with independent frequencies.

Although Mendelian genetics have been very useful in establishing the foundations of modern genetics, it is not very useful today. Without the use of molecular tools, it is very difficult to establish the range of action of a gene, since many characters are polygenic and are explained by more than two alleles (such as eye color, encoded by more than 3 genes).

2. Molecular Genetic

As its name indicates, molecular genetics is the branch of this discipline that studies the structure and functionality of genes at the molecular level, using techniques such as PCR (Polymerase Chain Reaction) or DNA cloning in the environment bacterial. In other words, is in charge of the investigation, description and management of the physical and functional unit of inheritance: the gene.

3. Developmental genetics

In this case, genetics is used to describe the process by which a cell ends up developing into a complete and functional multicellular being. It is responsible for investigating what conditions (at the nuclear and gene level) that a cell specializes throughout development in one function or another, among other things.

4. Population genetics

In the natural world, genetic viability is usually much more important than the population numbers that a species presents in a given ecosystem. If there are 500 animals in a specific nucleus but only 4 reproduce each year, there is a tendency to reduce variability and, therefore, to homozygosity.

As a general rule, homozygosity and inbreeding are associated with a more fatalistic prognosis in a population, since the little variability in the genes implies that responses to the environment will be very similar between animals, for good and for ma, in addition to a higher rate of accumulation of mutations deleterious. The effective population number, the percentage of heterozygosity, the allelic frequencies and many other things are quantified in the studies of population genetics for dtie the "welfare" of a species, beyond the number of copies.

• You may be interested in: "Genetic drift: what is it and how does it affect biological evolution?"

5. Quantitative genetics

Referring to previous points, quantitative genetics studies those phenotypes (traits encoded by genotype) that cannot be classified with typical Mendelian criteria, that is, by a dominant allele (A) and another recessive (a).

A very clear example of this is skin color, which is encoded by the TYR, TYRP1, OCA2, SLC45A2, SLC24A5 and MC1R genes, as well as environmental parameters and lifestyle. When a trait is polygenic or oligogenic, the approach must be very different.

6. Phylogeny

It is the branch of genetics that studies the kinship between the different taxa of living beings, creating in the process the famous "trees of life", which are used to group species into families, genera and species (also subfamilies, subspecies, tribes, etc.). DNA (nuclear or mitochondrial) and RNA sequences from tissue samples can help biologists evolutionary to infer kinship between living beings that, initially, have nothing to do at the level external.

• You may be interested in: "Phylogeny and ontogeny: what they are and how they differ"

7. genetic engineering

Genetic engineering is based on the direct manipulation of the genes of an organism, either with injections into culture media, with the transfer of mutated viruses or with many other mechanisms of transmission of information.

The objective of this branch of science is usually to improve the productive capacities of the species (especially in the agricultural environment), in order to grow faster, the product of better quality, the resistance of the crop is greater or that it is not affected by pests, among others things.

8. Epigenetics

The epigenetics is a very novel split from classical genetics, whose role is to explore the mechanisms that inhibit or promote the expression of genes throughout the life of the individual without producing changes in their genome.

There are several ways in which a gene can be "inactivated" temporarily, and these are mediated by genome sequences that were initially believed to be useless. Epigenetics, although in its infancy, promises answers to many headaches that today seem to have no solution.

Resume

As you can see, genetics is applicable to practically all fields of life. From the maintenance of ecosystems to the resolution of diseases, through the study of evolution, improving crops or understanding human fetuses, everything around us is determined by our genes.