It’s In The Genes - Understanding Heredity and Genes

“It’s in the gene’s.” It’s a common enough statement these days, but what are genes and how much do they really predict?  The whole of a person is made up of millions and millions of tiny cells which function in different ways in groups called tissue but are linked by carrying the exact same sequence of DNA, deoxyribonucleic acid, in each.   DNA is made up of codes sequenced from 5 different organic chemicals called nucleotides.  Genes are unique sequences of these nucleotides which serve as a blueprint for the cellular machinery to construct the various structural and functional parts of cells and therefore our bodies.  Every cell of a unique person carries the same sequences, and in each person they are slightly different. 


Even though each cell has the same sequence of DNA, the remarkable thing is that each cell uses that DNA in a different way.  Imagine a massively long list of words, and each word is a code that means something; the words are like genes - they mean something - but only if you know what to do with them and how they fit together.   The amazing thing is that each cell knows how to use this massively (almost impossibly) long list in its own specific way to make the proteins and enzymes that it needs.  Our DNA is like the letters or alphabet on the list, and the genes are how the letters combine.  DNA is organized into chromosomes which are predictable groupings of genes.  There are two copies of every gene and chromosomes are linked in pairs with matching genes on each.    


We have learned a great deal about how many human traits and characteristics are passed on to children and how the the DNA in each cell functions. The discovery of these genes supplied a lot of information regarding the ‘nature’ side of the nature vs nurture understanding of how and why human beings develop into the unique personalities with various health profiles.  The idea that much of our health and personalities were coded in DNA gathered a lot of momentum and led to the phrase mentioned at the beginning “It’s in your genes” being used frequently and at times in a fatalistic way meaning there wasn’t anything you could do to modify the risks for health issues.   


There are definitely many genes that are specifically passed on, and you have no choice but to inherit them.  For example if both your parents and their parents had black or white skin a baby would almost for sure be born with black or white skin.  There are also genes (or more specifically abnormal genes) that code for certain disease like Huntington’s Chorea and polycystic kidney disease, which if you possess  there is a 50% chance your children will inherit it and become ill with the same condition.  These are called autosomal dominant genes which means the genes are part of the chromosomes which are not involved in determination of sex and that you need only inherit one copy of the problematic gene to become sick.   There are also autosomal recessive genes which require two copies of the genes to cause a problem (ie having 2 chromosomes with the problem vs one).   As you can see there is certainly a lot to understanding genetics and inheritance.  Over the last number of years the genetic field of epigentics has become more and more prominent and is the biological basis, at least in part, explaining the nurture side of the Nature vs Nurture.  It is a fascinating field that is giving us incredible insights into the inheritance of lifestyle and chronic disease.  The most exciting thing is that, unlike the genes mentioned above, the epigentic landscape is highly modifiable.