Genetics
Genetics can be viewed as the branch of biology that is concerned with the study of heredity – dealing with the genetic properties. Modern genetics has expanded way beyond mere inheritance to now also study the function and behavior of genes and their environment.
Genetic inheritance
Each cell in the body contains 23 pairs of chromosomes. One chromosome from each pair is inherited from one’s mother and the other chromosome is inherited from one’s father. These chromosomes in return contain genes, in which there are two copies of every single gene, one copy inherited from each parent. (“Genes” are described as heritable units)
The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of a chain of molecules called nucleotides. The complete assembly of DNA is what makes every individual unique.
DNA can be viewed as the “recipe” for the production of proteins in cells, as it contains the nucleic acid code for cellular differentiation, function and replication.
The sequence of nucleotides in a gene is interpreted inside cells to produce a chain of amino acids, which in turn forms into a protein. Proteins carry out many of the functions that cells require to function.
A gene can also be viewed as a portion of DNA that gives “instructions” to execute a particular function or process in cells.
Genetic mutations
Genetic mutations occur when DNA changes and alters the genetic instructions. Mutations can for example occur when DNA is not copied accurately with cell division, or by exposure to specific chemicals or radiation. Mutations may either have no effect, or improve a protein and be beneficial, or even result in a protein that does not work and may cause a particular disease.
Simply put, genetic mutations are “spelling errors” in one or both copies of a gene that was inherited from your mother and your father. Some mutations may cause genetic disorders that results in various diseases.
However, genes generally cause very few health problems – most are caused by a combination of genes and environmental factors, including lifestyle choices.
The Human Genome Project
In 1990 an international research project kicked off with the objective of doing the complete mapping and understanding of all the genes found in human beings. (All our genes together is known as the “genome”.) The findings of this project have resulted in a resource of detailed information about the structure, organisation and function of the complete human genome.
This project has prompted further research in specific specialised areas of genetics, with some scientists claiming that “the new frontier” is not in outer space, but inside the body!
The human microbiome – the second genome
Microbes are everywhere around us, they even cover every surface inside and outside of our bodies. And they too have genes, outnumbering the genes in our genome by about 100 to 1. The assembled genes of all the microbes in our body is called the microbiome.
There are more than an estimated 100 trillion of these microbes in the human body, and they have numerous functions that are vital for to our bodies. Examples of these are the digestion of food and maintaining an impermeable and healthy gastro-intestinal tract. (Also known as the “gut”).
Studying the microbiome is of particular interest to scientists – to determine how the microbiome interacts with itself and with our bodies, and how this impacts health and disease.
Epigenetics
The human genome is the complete assembly of DNA that makes each individual unique. The chemical processes initiated by the DNA (deoxyribonucleic acid) give the instructions to genes for building the proteins that carry out a variety of functions in a cell, as described in item 2 above. Genes constantly turn on or off, depending on the biochemical signals they receive from the body. When genes are turned on, they express proteins that trigger physiological responses elsewhere in the body. This multitude of chemical compounds that give instructions to the genome is called the epigenome. The field of study that explores the epigenome is called epigenetics.
Nutrigenomics
Nutrigenomics (nutritional genomics) is the field of study of the interaction between food and genes. An individual’s unique genetic profile plays a role in how we respond differently to nutrients in the food we eat. Diet can play an important role or even pose a serious risk in terms of medical conditions for some individuals. Genetic makeup can influence the way that food interacts with one’s genes in two ways – nutrients can affect the way one’s genes are expressed, but genes can also influence how one’s body responds to these nutrients.
The saying “You are what you eat’ certainly holds true in the case of your genes, as the quality and variety of nutrients play a major role in the way our genes operate – turning signals from our genes on or off.
The Exposome
The “exposome” refers to the impact of the environment on our genes and how these exposures relate to our health. The environment in which our genes live is just as important as the genes themselves. Our risk to diseases for example is to a large extent related to exposure to our environment and the resulting alterations in the molecules that interacts with our genes.
This field of study concerns itself with understanding how exposures from our environment, including lifestyle and diet, interacts with an individual’s unique genetic profile and the impact this has on one’s health. Our exposome includes all the factors that determine health and disease, such as toxins, nutrients, microbes and other internal chemicals that can affect the way our genes function.
Medical Genetics
This field of study is involved with trying to understand how genetic variations relate to health and disease. Scientist may for example search for an unknown gene that may be involved in a disease, or look for locations in the genome that are associated with a particular disease.
Genetics and exercise
Genetic expression can be altered by changes to various lifestyle factors, such as diet and exercise, by altering the types of proteins a particular gene will express. Exercise, for example, can result in immediate changes in the expression of genes found in the muscle cells and can lead to the genetic programming of muscles for strength. In the same way genes are involved in fat metabolism. Exercise also results in genetic activation that increases the production of fat metabolizing protein pathways.
Studies have shown that endurance training induces genetic alterations that promote good health, while high intensity interval training is even more effective in this regard. The increased blood flow to the brain that occurs during exercise triggers the brain to turn different genes on or off, and many of these changes can assist in protecting the brain against diseases such as Alzheimer’s and Parkinson’s disease.
HEALTH INSIGHT
MARCH 2017