What is DNA?
In 1953, James Watson and Francis cricks (Nobel prize winners) discovered the structure of DNA (deoxyribonucleic acid). In brief, DNA is double-stranded and has a helical structure like a spiral stairway. Each strand of DNA is a polymer composed of four different units, called nucleotide bases (cytosine, C; guanine, G; adenine, A; or thymine, T) (Snyder 2016). DNA strands store information for regulating functions of the cells and organs. By the way, the information hidden in DNA is determined by order of nucleotide bases assembles (just like information in a sentence or a paragraph of a book which is determined by order of letters). Amazingly, human DNA contains 6 billion nucleotide pairs (6000,000,000 pairs!).
What is a Chromosome?
As I mentioned above, DNA is very long; if it is stretched out end to end, it would be about 2 meters in length. But it is tightly packaged into elements, called chromosome, to fit inside a cell. So then, human DNA is packed into 46 chromosomes. As a rule, we inherit 23 of our chromosomes from mother and 23 from the father.
What are Genes?
The entire 6 billion base pairs of DNA is called genome. A gene is a part of DNA that instructs production a protein (Jain 2015). Human has between 20,000 to 25,000 genes. Genes have different sizes.
How can information hidden in our DNA be decoded?
In 1990, scientists started the Human Genome Project with the aim of defining the sequence of nucleotide bases and identifying the human genes. About 2000 researchers participated in this project, and it costs about $2.7 billion. Finally, in April 2003, the Human Genome Project completed sequencing of DNA, identifying more than 20,000 genes in our genome. As a result, today you have access to sequence of the DNA in databases on the internet (GenBank sequence database, https://www.ncbi.nlm.nih.gov/gene/?term=).
There are differences in each of our DNA that makes each person unique. Generally, Geneticists estimate that about 0.1% of DNA is different between two unrelated individuals (or maybe higher, 2-5 times). Today, it is possible to determine the sequence of an individual’s DNA (the strategy called DNA sequencing) in a few days and much cheaper than before ($600-$1000) to detect DNA variations. Also, there are alternatives to whole genome sequencing like the sequencing of a specific targeted gene or a panel of genes which cost even less (over $100) (Shendure et al. 2011).
Learn more about DNA variations and DNA testing kits?
The genome variations have different types, ranging from chromosomal rearrangements, alterations affecting a segment of DNA (called structural variations) to single nucleotide variations (SNVs) (Auton et al. 2015). For instance, if the human DNA is viewed as a book, then SNVs are like single letter changes in the book, whereas structural variations are equal to changes (inserting, deleting or repeating) of several words or paragraphs (Jain 2015). In summary, either these DNA variations lead to individual physical features (like the color of skin, height, weight, etc.), or they can cause diseases (called mutation). However, sometimes the impact of these variations is not known; it is not clear whether these variations are disease-causing (a mutation). Therefore, this makes DNA testing challenging for Geneticists.
Lastly, nowadays, you have heard about different DNA testing kits. For example, ancestry DNA testing kits, discovering where your DNA is from out, are very popular. Besides, there are health DNA test kits, predicting your risk for susceptibility to some diseases, like genetic testing for cancer, heart disease, or DNA testing for Alzheimer. Furthermore, DNA tests can also help to stay fit. Thereby they predict your nutritional needs, your proper diet to lose weight easier.
Additionally, they determine your individualized training plan and skin care to maintain your fitness. Above all, genetic labs provide you home DNA test kits which are comfortable and reliable. Then you can collect your saliva (or take a mouth swab) and send it to them to test your DNA.
– Snyder M. Genomics & personalized medicine. New York: Oxford University Press; 2016.
– Jain KK. Textbook of personalized medicine. New York: Humana Press; 2015.
– Auton A, Brooks LD, Durbin RM, et al. “A global reference for human genetic variation”. Nature 2015; 526 (7571): 68–74.
– Shendure JA, Porreca GJ, Church GM, et al. Overview of DNA sequencing strategies. Curr Protoc Mol Biol. 2011; 96(1): 7.1.1-7.1.23.
– Nussbaum RL, McInnes RR, Willard HF, Hamosh A. Thompson & Thompson Genetics In Medicine. Philadelphia: Elsevier; 2007.
– Wist AD, Berger SI, Iyengar R. Systems pharmacology and genome medicine: a future perspective. Genome Med. 2009; 1: 11.