DNA

What is DNA? Intro to Basics of Genetics

What is DNA? Intro to Basics of Genetics

We are sure that most of you have heard of deoxyribonucleic acid – a molecule present literally in every living being as a significant building block of life. Moreover, it is also known as a blueprint of life, as it stores all information for building our bodies. 

It is present in every human cell, and animals, plants, and even microorganisms like bacteria possess DNA. You may be surprised that some animals like dogs, chickens, or chimpanzees share a significant percentage of genetic makeup with humans. In fact, we share over 99% of our genes with chimpanzees, 84% with dogs,  65% with chickens, etc. [1, 2, 3]. 

Unless you are a genetics expert or familiar with life sciences, you may ask yourself here: "What is all that genetic stuff, and why is it so important?” Well, through the series of articles, we aim to guide you step by step, from explaining the basics of genetics to the whole procedure going from saliva sampling over DNA extraction, genotyping, quality control, and finally processing genotyping data and generating results. In this article, you will find out why DNA is called a blueprint of our bodies. 

What is DNA?

Just saying that DNA contains all necessary instructions for life is not enough. Therefore, we need to go a bit deeper into molecular aspects to explain the structure, location, and how is it used as a blueprint, dictating the development and growth of the organism.

Deoxyribonucleic acid is a polymeric double-stranded macromolecule. It means it is among the enormous molecules in our organism and composed of smaller biological building blocks called nucleotides [4]

Each nucleotide comprises three components – a nitrogen base, a phosphate group, and sugar called deoxyribose. These three together constitute what is called a backbone of a DNA strand [5].

DNA structure
Figure 1: Structure of DNA


The nitrogen base is perhaps the most important as it provides an identity to the nucleotide. Each nucleotide contains either of the following four bases: adenine (A), guanine (G), cytosine (C), or thymine (T)
[5].

Within the DNA molecule, adenine always pairs with guanine and cytosine with thymine. Two strands run in opposite directions and are linear in human cells. In contrast, DNA in bacterial cells is circular [4].

DNA is primarily known for its hereditary nature, as it contains our genes and all genetic information. However, it plays an essential role in other crucial life processes, and we will explain them briefly in the following articles.

Cell location

After you learn the structure, you may ask yourself where DNA takes place in the human body. As is the case with all eukaryotic cells, DNA is located in the nucleus. It is tightly packed into several structural forms, the last one being the most prominent and well-known– chromosomes. 

Within chromosomes, there are sections of DNA called genes that contain information that encodes proteins. There are also stretches of DNA sequences between genes. These are called intergenic regions and are a subset of noncoding DNA that mostly have a regulatory function, which means they control gene expression.

Each human individual contains a complete set of DNA, called the genome. The human genome contains 3 billion bases, around 30,000 genes, packed into 23 pairs of chromosomes, where each pair is inherited from either parent [5].

How does information stored in DNA build life? 

The primary function of DNA is to provide a cell with the code or instructions on how to make proteins. Proteins will further determine our appearance and traits. However, if there is a change in DNA, it will cause a change in the final protein product, which may lead to disease. Although it may sound simple to you, this is a very complex process and is a matter of study for molecular biology. 

Central dogma of molecular biology

Figure 2: Schematic representation of central dogma

The blueprint of DNA follows the rules of the central dogma, which is the central term in molecular biology. This process explains how to get from DNA to protein via another nucleic acid, called ribonucleic acid (RNA) [6]. As illustrated in Figure 2, it is a process that consists of two stages:

(i) Transcription  

(ii) Translation

The synthesis of proteins happens on ribosomes located in the cytoplasm outside the nucleus. But DNA has to go through several steps before synthesis.

First, DNA strands have to split apart. Each strand serves as a matrix for synthesizing RNA molecule that has a similar structure to mold DNA molecule but has a single strand. All genetic code contained in DNA is safely transcribed to single-stranded RNA.

RNA carries a message from DNA to cellular machinery in the cytoplasm that reads the message three base pairs at a time and translates them into amino acids that assemble a protein as a final product [6].  

What if things in DNA go wrong?

As we have already explained, our cells read instructions from DNA to produce essential proteins for survival and all-important life functions. Different combinations of amino acids constitute proteins. 

When the correct set of amino acids is in the right order, then the protein has its proper structure and function in our bodies. However, as everywhere in life, errors happen even on a molecular level. These are called mutations and can occur due to errors in DNA replication or be caused by biological or chemical agents. However, it is essential to emphasize that mutations are one of the key evolutionary forces, making us different, despite the huge amount of shared DNA.

The fact is that our DNA is very prone to damage and mistakes. There is an estimate of 175 mutations happening per human genome per generation [7]. Errors occur all the time our cells undergo replication. You may now ask how we are still alive and function correctly besides all these errors inside us.

Well, the good news is that our cells possess well-trained and sophisticated proofreading mechanisms that read your DNA and immediately repair any damages. However, sometimes not all damages get repaired. They proceed, causing various diseases sometimes, like cystic fibrosis or sickle cell anemia, caused by a single gene mutation. In one of our following articles, we will tell you more about mutations.   

Meet Biocertica DNA test

BioCertica DNA saliva kit

Figure 3: BioCertica DNA kit

To find whether your genes carry any mutations and how they influence your health and life, you must get your DNA extracted, genotyped, sequenced, and analyzed. 

At BioCertica, we analyze your whole genome. However, it's not the case only with us but also with all companies aiming to discover your ancestry, create a better nutrition plan for you or discover your risk for certain diseases.  What distinguishes us from others is the wide variety of DNA kits available and the fact that your identity and data are safeguarded and secured, being always available to you. You can check or purchase our products here.

In our next article, we will talk about the importance of DNA to our health and introduce you to the importance of DNA tests. Stay tuned!

References

  1. Mikkelsen, T., Hillier, L., Eichler, E., Zody, M., Jaffe, D., Yang, S. P., ... & Waterston, R. (2005). Initial sequence of the chimpanzee genome and comparison with the human genome. Nature, 437(7055), 69-87.
  2. International Chicken Genome Sequencing Consortium. (2004). Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution. Nature, 432(7018), 695-716.
  3. Kirkness, E. F., Bafna, V., Halpern, A. L., Levy, S., Remington, K., Rusch, D. B., ... & Venter, J. C. (2003). The dog genome: survey sequencing and comparative analysis. Science, 301(5641), 1898-1903.
  4. Al Aboud, N. M., Basit, H., & Al-Jindan, F. A. (2019). Genetics, DNA Damage, and Repair. 
  5. Ghannam, J. Y., Wang, J., & Jan, A. (2020). Biochemistry, DNA Structure. StatPearls [Internet].
  6. Cobb, M. (2017). 60 years ago, Francis Crick changed the logic of biology. PLoS biology, 15(9), e2003243.
  7. Nachman, M. W., & Crowell, S. L. (2000). Estimate the mutation rate per nucleotide in humans. Genetics, 156(1), 297-304