What is Genomics?

What is Genomics?
Genomics is the discipline that aims to decipher and understand the entire genetic information content of an organism.

Genomics uses a combination of recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyse the structure and function of genomes. It differs from ‘classical genetics’ in that it considers an organism’s full complement of hereditary material, rather than one gene or one gene product at a time.

Background theory:
Genetic information: It means information contained with DNA (deoxyribonucleic acid) and RNA (ribonucleic acids).

About genes
Our body is made up of billions of cells with instructions for how our body should grow and function. These instructions are contained in your DNA – deoxyribonucleic acid – and DNA is packaged into structures called chromosomes.

our DNA contains stretches of genetic code, which are called genes. Each gene gives an instruction to the body. For example, a gene may be an instruction about eye colour. You usually have two copies of each gene, one inherited from each of your parents.However, if there is a mistake in one of these genes, it may not work properly.A genomic sequencing test examines sections of your DNA for changes that may alter the genes and lead to disease.

What is DNA?
Deoxyribonucleic acid (DNA) is the chemical compound that contains the instructions needed to develop and direct the activities of nearly all living organisms. DNA molecules are made of two twisting, paired strands, often referred to as a double helix

Each DNA strand is made of four chemical units, called nucleotide bases, which comprise the genetic “alphabet.” The bases are adenine (A), thymine (T), guanine (G), and cytosine (C). Bases on opposite strands pair specifically: an A always pairs with a T; a C always pairs with a G. The order of the As, Ts, Cs and Gs determines the meaning of the information encoded in that part of the DNA molecule just as the order of letters determines the meaning of a word.

What is a genome?
An organism’s complete set of DNA is called its genome. Virtually every single cell in the body contains a complete copy of the approximately 3 billion DNA base pairs, or letters, that make up the human genome.

With its four-letter language, DNA contains the information needed to build the entire human body. A gene traditionally refers to the unit of DNA that carries the instructions for making a specific protein or set of proteins. Each of the estimated 20,000 to 25,000 genes in the human genome codes for an average of three proteins.

Located on 23 pairs of chromosomes packed into the nucleus of a human cell, genes direct the production of proteins with the assistance of enzymes and messenger molecules. Specifically, an enzyme copies the information in a gene’s DNA into a molecule called messenger ribonucleic acid (mRNA). The mRNA travels out of the nucleus and into the cell’s cytoplasm, where the mRNA is read by a tiny molecular machine called a ribosome, and the information is used to link together small molecules called amino acids in the right order to form a specific protein.

Proteins make up body structures like organs and tissue, as well as control chemical reactions and carry signals between cells. If a cell’s DNA is mutated, an abnormal protein may be produced, which can disrupt the body’s usual processes and lead to a disease such as cancer.

Each plant, animal or bacteria carries its entire genetic code inside almost every one of its cells

Sequencing
Genomics harnesses the availability of complete DNA sequences for entire organisms and was made possible by both the pioneering work of Fred Sanger and the more recent next-generation sequencing technology.

Sequencing simply means determining the exact order of the bases in a strand of DNA. Because bases exist as pairs, and the identity of one of the bases in the pair determines the other member of the pair, researchers do not have to report both bases of the pair.

In the most common type of sequencing used today, called sequencing by synthesis, DNA polymerase (the enzyme in cells that synthesizes DNA) is used to generate a new strand of DNA from a strand of interest. In the sequencing reaction, the enzyme incorporates into the new DNA strand individual nucleotides that have been chemically tagged with a fluorescent label. As this happens, the nucleotide is excited by a light source, and a fluorescent signal is emitted and detected. The signal is different depending on which of the four nucleotides was incorporated. This method can generate ‘reads’ of 125 nucleotides in a row and billions of reads at a time.

To assemble the sequence of all the bases in a large piece of DNA such as a gene, researchers need to read the sequence of overlapping segments. This allows the longer sequence to be assembled from shorter pieces, somewhat like putting together a linear jigsaw puzzle. In this process, each base has to be read not just once, but at least several times in the overlapping segments to ensure accuracy.

Researchers can use DNA sequencing to search for genetic variations and/or mutations that may play a role in the development or progression of a disease. The disease-causing change may be as small as the substitution, deletion, or addition of a single base pair or as large as a deletion of thousands of bases.

Advantages
Genomic sequencing offers huge benefits. It is currently being used to predict disease risk, diagnose patients, and guide treatment, and its use is expected to grow exponentially in coming years as science and technology continues to advance healthcare.Genomics is driving the emerging field of ‘precision medicine’, which involves treating individual patients based on the particular genetic causes of their cancer, as opposed to uniform approaches to treatment like chemotherapy. Patients will receive individualised targeted treatment options with a smaller amount of side effects and focused treatment timeframes.Genomic sequencing can also identify the cause of rare genetic diseases in children, who may otherwise be undiagnosed.

Challenges
However, while it offers huge benefits, genomic sequencing also presents a range of challenges. The research and technology is progressing rapidly, which means the information gained is moving faster than our knowledge about how it will affect our lives. While the issues can be addressed and overcome, it’s crucial that we consider them to make sure patient wellbeing is the priority.