What is DNA? The Basics of Genetics

What makes you who you are? A psychologist might have a different answer, but in the world of biology, we'd say it's deoxyribonucleic acid or as you may know it as DNA. DNA is the fundamental molecule needed for living things. Moreover, we can also consider DNA as the blueprint of life, because it stores all information for building our bodies. 

DNA as the Blue Print of Life 

We are sure that most of you have heard of deoxyribonucleic acid (DNA) – 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, animal cells, plants cells, and even microorganisms like bacteria possess DNA.

Just saying that DNA contains all the 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 it is used as a blueprint, dictating the development and growth of the organism via the central dogma of molecular biology - the flow of genetic information from DNA to protein.

Deoxyribonucleic acid is a polymeric double-stranded macromolecule composed of smaller biological building blocks called nucleotides [1]. Each nucleotide comprises three components – a nitrogen base, a phosphate group, and sugar called deoxyribose. The sugar and the phosphate constitute what is called a backbone of a DNA strand (Figure 1) [2].

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) [2].

Within the DNA molecule, adenine always pairs with thymine and cytosine with guanine. Two strands run in opposite directions and are linear in human cells. In contrast, DNA in bacterial cells is circular [1].

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.

DNA location and inheritance 

As is the case with all eukaryotic cells, DNA is located in the nucleus. It is tightly packed into several structural forms, the most compact of which is known as a chromosome.


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 one chromosome from each pair is inherited from either parent [2].

Each individual has 22 pairs of autosomal chromosomes and one pair of heterosomes (sex chromosomes) that can be either XY for males or XX for females (Figure 3). A karyogram is a visual representation of individual chromosomes, where homologous (matching) chromosomes are arranged and divided into groups by decreasing size.

However, DNA is not only located in the cell’s nucleus. DNA can also be found in the mitochondria, a special organelle in the cell responsible for creating energy. This DNA is known as mitochondrial DNA (mtDNA) and can only be passed down through the maternal line. Additionally, Y chromosome DNA (YDNA) is characteristic of the Y chromosome present in men and is inherited only from paternal lineage.

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. Although it may sound simple, this is a very complex process and is a matter of study for molecular biology.

The blueprint of DNA follows the rules of the central dogma. This process explains how to get from DNA to protein via ribonucleic acid (RNA) [3]. As illustrated in Figure 5, it is a process that consists of two stages:

(i) Transcription – the process by which RNA is made using DNA as a template.
(ii) Translation – the process by which protein is made using RNA as a template.

RNA carries a message from DNA to cellular machinery in the cytoplasm that reads the message (called a ribosome). Every three base pairs in the RNA (known as a codon) corresponds to an amino acid, the building block of protein. The ribosome moves along the RNA strand and assigns the corresponding amino acid to each codon to create a chain of amino acids that will later become the final protein product [3].

You can think of the central dogma as a process for making your grandmother’s famous chocolate cake. Your grandmother has the original copy of the recipe (this is like the DNA), and in order to keep that copy safe, you don’t take it from her but rather copy it (this is like the RNA). From your copy of the recipe, you can make your own chocolate cake (this is like the protein).

What if things in DNA go wrong?

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 [4]. Errors occur all the time when our cells undergo replication. However, for the most part, our cells can catch and correct these errors. 

 Meet Biocertica DNA test

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!

Written by: Nermin Đuzić, M.Sc. in Genetics, Content Specialist

References

[1] Al Aboud, N. M., Basit, H., & Al-Jindan, F. A. (2019). Genetics, DNA Damage, and Repair.

[2] Ghannam, J. Y., Wang, J., & Jan, A. (2020). Biochemistry, DNA Structure. StatPearls.

[3] Cobb, M. (2017). 60 years ago, Francis Crick changed the logic of biology. PLoS biology, 15(9), e2003243.

[4] Nachman, M. W., & Crowell, S. L. (2000). Estimate the mutation rate per nucleotide in humans. Genetics, 156(1), 297-304