Deoxyribonucleic acid or DNA is the blueprint for all the inherited characteristics that are present in living things. It is a long sequence which is written in code which needs to be transcribed and translated so that a cell can make the proteins which are essential for the life processes. Any kind of changes in the DNA sequence could lead to changes in the proteins, and, in turn, they might translate into the changes in the traits that those proteins can control. Changes at the molecular levels tend to lead to the micro-evolution of species. In this article, we will take a look at what is DNA, the significance of DNA and the significance of DNA in evolution. Let us first learn about what is DNA and how it works in the several life processes of the human body.
The DNA which is present in the living things is highly conserved. DNA consists of four different nitrogenous bases which code for all differences in the living things present on the Earth. Adenine, cytosine, guanine, and thymine are the for nitrogen bases that line up in a specific order. A group of three, or one codon, code for one of the total 20 amino acids that are found on Earth. The order of these amino acids determines what type of protein is made.
Remarkably enough, only four of the nitrogenous bases which make just 20 amino acids account for all of the diversity of life on Earth. No other code or system has been present or found in any of the living or once-living organisms on Earth. Organisms ranging from bacteria to humans to the dinosaurs all have the same type of the DNA system as a genetic code. This can point to evidence that all types of life evolved from just one single common ancestor.
All of the cells are pretty well-equipped with the way for checking a DNA sequence for any kind of mistakes before and after the process of cell division, or mitosis. Most of the mutations, or changes in the DNA, are caught before the copies are made and these cells are destroyed. However, there are some times when even the small changes do not make much of a difference and would pass through the checkpoints. These mutations can add up over a period of time and change some kind of the functions of that particular organism.
If these mutations occur in the somatic cells, in simpler words, the normal adult body cells, these changes would not affect the future offspring. If the mutations occur in the gametes, or sex cells, the mutations would get passed down to the offspring generation and might affect the different functions of the offspring. The gamete mutations would lead to microevolution.
Our genes tend to determine our bodies. They provide us with the biological information which makes us who we are today. Although the future developments in science and medicine might allow us to change the parts of ourselves, presently we cannot make any changes to our genetic code. For example, you cannot change the genes which provide you with your natural hair colour. Instead, if you want to change your hair colour, you would have to colour or dye it. The same thing is true for so many disorders and diseases which have a genetic origin. You cannot change those genes once you inherit them from your parents.
Genes can also determine a few parts of your personalities. Researchers have demonstrated that genes can relate to our sexuality, the development of certain addictions, how our moods tend to change, and several other elements of human psychology. However, if you know about any identical twins, you would be already able to realize how difficult these studies are. Even when they have the same genetic code, the identical twins often tend to form varying personalities. However, a lot still remained to be learned in this field.
Even though the earlier theories that were related to genetic determination said that all human features were coded by genes, modern scientists understand the fact that environment also tends to play a role in forming several of our physical traits, personality traits and characteristics, and illnesses. Additionally, the epigenetic effects might cause the genes to turn on and off, downregulate, or upregulate. Changing the way how a gene is expressed would change the trait that is produced, even if the basic DNA sequence of the gene does not change.
1. What is the Evidence for DNA Being Involved in Evolution?
DNA has only been understood over the past century. The technology is improving and has allowed the scientists to not just map out the entire genomes of different species, but they also use computers for comparing those maps. By entering the genetic information of the different species, it is easier to check where there is an overlap and where there are differences.
The more closely the species are related to each other on the phylogenetic tree of life, the more closely their DNA sequences would overlap. Even the distantly related species would have some degree of the DNA sequence overlap. Certain proteins are required for even the most basic processes of life so that the selected parts of the sequence which codes for those proteins would be conserved amongest all the species on Earth.
2. What is DNA Sequencing and Divergence?
Now that the DNA fingerprinting has become quite easier, efficient and cost-effective, the DNA sequences of a huge variety of species can be easily compared. In fact, it is even possible to determine the time when the two species diverged or branched off via the speciation. The larger the percentage of the differences in the DNA amongst two different species, the greater is the amount of the time the two species would have been separate.
These molecular clocks are used for filling in the gaps of the fossil record. Even when there are certain missing links in the timeline of the history on Earth, the evidence of the DNA could give clues as to what would have happened during those times. While the random mutation events might throw away the molecular clock data at some specific points, it is still an accurate measure of the time when the species would have diverged and became new species.