The term ‘genetic disease’ is a blanket name for all diseases arising from a defect or damage in the gene, i.e. DNA.
Examples of genetic diseases include sickle cell anaemia, hemophilia (a bleeding disorder), achondroplasia (the big-head dwarfism), colour blindness, cancers, etc.
Not every genetic disorder is inheritable; however, all hereditary disorders are genetic disorders because they all originate from a fault in the structure, number or presence of genes. Let me explain using cancers.
A skin cancer resulting from high-dose radiation to the skin is a genetic disease because a damage occurred in the DNA of the skin cells at the exposed part before they ran mad and started multiplying uncontrollably.
Of course, the sufferer did not inherit a gene for that cancer from their parent(s) neither will they pass a gene for it to their own children. So, that skin cancer is a non-hereditary genetic disease.
Before a gene mutation can be passed from a parent to their offspring, that mutation must have affected cells that eventually become sperm cells in men or eggs in women. These cells are called ‘germ cells’ and the mutation germline mutation.
Hereditary diseases are genetic diseases arising from mutation in the DNA of germline cells. That is, the damage to DNA happened along the line of formation of sperm cells or eggs.
Conversely, non-hereditary genetic diseases arise from mutation in body cells which do not take part in the reproductive process. The skin cancer example above should suffice.
You should know, however, that some cancers are hereditary, too. Examples: some breast cancers, ovarian cancer, colon cancer, prostate cancer, etc.
We say these cancers are hereditary because there are some inherited gene faults that make it far much easier for the bearers of those genes to develop these cancers.
There are a number of important human genes that tell our bbody cells to produce specific proteins that regulate and control cell growth and multiplication.
Two notable ones are BRCA1 and BRCA2 genes implicated in the causation of breast, ovarian and prostate cancers.
A mutation in either of these genes can be passed from a parent to an offspring. Since the gene is now faulty, the regulator protein it should produce is now absent and this increases the chances of these cancers by multiple folds.
This is why female individuals whose mothers’ suffered a breast cancer are far more likey to have the same disease later, hence the need for increased surveillance.
Research has shown that up to 7 out of 10 women with BRCA gene defect will have cancer before the age of 80 years.
The beautiful American actress Angelina Jolie had to surgically remove her two breasts when she was diagnosed with BRCA defect.
There is a gene called Adenomatous Polyposis Coli (FAP) gene, a defect in which is responsible for the growth of too many polyps in the large intestine of people who inherit the gene defect.
Family members diagnosed with too many otherwise harmless polyps in the large intestine are usually advised to cut off part of their large intestine to prevent the polyps from turning to colonic cancer. .
These kinds of decision are difficult yet they are necessary to forestall future health tragedies.