What Are Genes? Genes are closely associated with other concepts such as chromosomes and DNA. Discover what they are
Between the years 1857 and 1864 the scientist Gregor Mendel discovered that the pea plants he studied possessed distinctive traits that were inherited from one another. He was faced with the phenotypic expression of genes, but it was not until 1905 that the term “gene” was introduced into the scientific vocabulary.
From the time of Mendel to the present, genetics (the science that studies the biological inheritance) has advanced a lot, but there is still another much to discover.
Throughout this article, we will discover what genes are, what their functions are and how they are associated with DNA and chromosomes, among other key concepts of genetics.
What are genes?
In the field of biology, genes are a section of DNA (deoxyribonucleic acid) that carries out different functions such as, for example, the manufacture of proteins. The long strands of DNA that make up many genes make up the chromosomes, and these are located inside the nucleus of each cell.
During genetic expression, DNA is first copied into RNA. RNA or ribonucleic acid is a polymeric molecule that has an essential role in various biological functions such as coding, decoding, regulation and expression of genes.
RNA and DNA are nucleic acids that, together with lipids, proteins and carbohydrates, constitute the four main basic macromolecules to be able to constitute all known life forms.
The transmission of genes to the offspring of any organism, human or not, is the basis of the inheritance of phenotypic traits. These genes form different DNA sequences known as genotypes. These sequences, together with environmental and developmental factors, determine what the phenotypes will be. That is to say, those physical characteristics perceptible to the eye, such as the color of eyes or hair.
In genes, different types of mutations can occur in their sequence, giving rise to variants known as alleles. The alleles encode subtly different versions of the one protein, which gives rise to different phenotypic characteristics and, at times, are the basis of some genetic diseases.
Over the years and the progress of research, the concept of “gene” has been refined and continues to change as different discoveries are made. Therefore, a general and updated definition of this term refers to the gene as a locus of hereditary genomic sequence that, when expressed, affects the features of an organism.
What are genes made of and what is their function?
A genes consists of a long combination of four different nucleotide bases. These nucleotides are chemical products that can be combined in a myriad of ways.
The different combinations of these letters grant living organisms their particular characteristics. In the case of people, a specific combination can result in the person having blue eyes, while a different combination is expressed with brown eyes.
Genes determine almost all the characteristics of a living being. Each of the genes can affect a specific trait, both visible and non-visible, and can interact or be influenced by the environment by changing what the gene produces and the way in which it is expressed.
For example, genes “decide” hundreds of internal and external factors such as a particular color of hair or skin, but also, a variety of genetic or inherited diseases that the person can develop.
What are DNA and chromosomes?
As mentioned in the first point, the concept “gene” is closely associated with the terms “DNA” and “chromosomes”. Now, do we know exactly what both concepts consist of and what is their relation to the genes?
Deoxyribonucleic acid (DNA)
The vast majority of living organisms have their genes encoded in long strands of DNA. DNA consists of a chain composed of four types of nucleotides, each with a sugar, a phosphate group and one of the four nucleotide bases named above.
Two strands of DNA spin around each other to form the famous DNA double helix. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds, while cytosine and guanine make up three of these same bonds.
Therefore, the two strands that make up the DNA must be complementary, making their base sequences coincide so that the nucleotides of the one strand match correctly with those of the other, and so on.
The total set of genes in an organism or a cell is known as a genome, which is stored in one or more chromosomes. A chromosome consists of a single very long DNA helix in which thousands of genes are encoded.
The region of the chromosome in which a particular gene is found is called a locus and each locus hosts an allele of a gene. However, these alleles do not have to be the same in all organisms. Members of a population may have different alleles at a locus, each with a slightly different gene sequence.
Chromosomes store hereditary information for everything from height to eye color. In most organisms, humans, animals, and plants, the chromosomes are arranged in pairs within the nucleus of a cell.
People have an extra pair of sex chromosomes, which implies that we have a total of 46 chromosomes: 22 pairs called autosomes and a pair of sex chromosomes that are known as X and Y, which determine the biological sex of the person.
While the female sex is determined with the XX chromosomes, the male does with the XY chromosomes. This sex-determination system is also found in most mammals, reptiles, and plants.
The human genome
In the previous section, we mentioned that all the DNA of a cell makes up the genome, and this also applies to people. It is estimated that there are approximately 20,000 important genes located in one of the 23 pairs of chromosomes found in the cell nucleus.
The DNA of the genes constitutes only 2% of the human genome. Since 1990, each of the discovered gene sequences is recorded meticulously in terms of their specific location, sequences, etc. All this information is stored in a public access database that is part of the well-known Human Genome Project.
Human Genome Project is the largest research project of modern science. The objective of this project is to determine the sequence of the chemical pairs that make up the DNA of people, as well as identify and map the 20,000 genes that make up our genome.
This is expected to provide researchers with the necessary tools to understand the genetic factors of human diseases, as well as open a door for new diagnostic, treatment and prevention strategies.
The Human Genome Project was completed in 2003, having found more than three billion combinations of nucleotides – that is, more than three billion combinations that make up the collection of genetic characteristics that can form the human body.