What is genomic sequencing ?
What is DNA, what is a gene, what is a protein... ? Take a tour on the basics of genetics here (Genetics Scisnce Learling Center; University of Utah)
1. From Cells to proteins: Introduction to DNA


All living organisms, including humans, are composed of cells. Cells are complex systems composed of many different building blocks enclosed in a membrane. The human body is estimated to be composed of about 6x10^13 cells, of about 320 different types.
Basic Cell structure.  Source


 Cell size may vary depending on the cell type and on circumstances: For instance, a human red blood cell is about 5 microns (0.005 mm) in diameter, while some neurons are about 1 m long (from spinal cord to leg). Typically the diameter of animal and plant cells are between 10 and 100 microns.





1. Red Blood cell. Source;

2. Neurons Source;

3. Glyoma cell Source

Cells that compose the human have a nucleus, which is separated from the rest of the cell by a membrane. The nucleus contains DNA, the carrier of the genetic material. In each cell nucleous there are several long double stranded DNA molecules composed of a long chain of small molecules called nucleotides. There are four different nucleotides: adenosine, guanine, cytosine and thymine. They are denoted by their initial letters, A,C ,G and T and form complementary pairs: A-T and C-G. They are usually referred to as 'base pairs'.
gene is a localised and continuous stretch of DNA molecule, from which a complex molecular machinery can read information (encoded as a string of A, T, G, and C) and make a particular type of a protein or a few different proteins. Proteins are an extremely diverse group of molecules that are required for the structure, function, and regulation of the body's cells, tissues, and organs. Each protein has unique functions in our body. Proteins are essential components of muscles, skin, bones and the body as a whole.
 Protein structure Source
Examples of proteins include whole classes of important molecules, among them enzymes, hormones, and antibodies.

Proteins are composed of a chain of small molecules called 'amino acids'. The translation of DNA to proteins is a complex biochemical process, but is following a very straightforward code, called 'the Genetic code'. Each series of three base pairs codes for one amino-acid, basic components of proteins.

2. Reading our body functions code: Introduction to genomic sequencing.
Genomic Sequencing technologies enable us to read the complete sequence that compose the genome of an individual. This genome is absolutely unique to each single living organism, and is believed to encode all our hereditary information. The complete genome sequence can hence be used for identification purposes, like in crime scenes. All cells in an organism contains the complete genome of the individual, hence we can use a wide variety of cells to do genomic sequencing. The size of genomes greatly varies among species: the human genome is composed of 3 thousand million base pairs, whereas bacterial genomes range from 400 thousand to 10 million base pairs.
 Sequencing of the relatively small bacterial genomes has become routine and is largely done by sequencing robots and completed by human researchers, the main leitmotiv being the minimisation of costs per letter, and maximisation of the speed while maintaining quality. Sequencing of larger genomes, like a human genome, can now be done by one 'Next Generation Sequencing' machine within a week and for a cost of about 10.000$. 

3. The use of Genomic Data in Research
Numerous genetics research projects include the sequencing of human genomes. These studies try to determine, thanks to the information contained in the genome, the origin and characteristics of diseases affecting us, from cancer to Alzheimer's disease, and to rare diseases. Indeed, changes in the genome, known as 'mutations' can cause disease, and/or affect one's susceptibility or response to a disease. Some research teams sequence genomes of patients from the clinical context, and some others from controls (people not affected by a particular disease) in the general population. The biological samples as well as data from each participant (identification data -name, address- and lifestyle/medical data -special diet, allergies, smoking habits) are stored in databases called 'biobanks'. Each individual participating to a research signs a 'consent form' where the conditions of use of his biological samples and his personal data (identification or medical) are described. (Who can have access to his samples/data and under which conditions).