Genetics experts tell us that the human being has a basic unit; that is to say in basic terms, a container having within it a very rich content. Something inside which is found everything necessary for the proper functioning of the human organism. And this thing is human cells. According to experts, each human being has around 70,000 billion cells which have different functions and roles. And what is inside the cells? Inside we have a nucleus which plays the role of a central unit and inside which there is a genetic heritage of each human being formed by 23 pairs of chromosomes, that is to say, 23 multiply by two or forty-six chromosomes per person. When an ovum is fertilized following an interaction between sperms and ovums which themselves reside in cells called gametes, responsible for sexual reproduction, the future child receives half of his father's genetic heritage who has 46 chromosomes, and half of the heritage of his mother who also has 46. That is to say, 23 on both sides. This means that a child’s inheritance begins at the stage of conception. However, chromosome mix and external influences can cause a protein to change, altering its function to the point of causing disease. Let us clarify that a gene is a fragment of DNA with a specific function. It allows the production of specific proteins, responsible for a specific function in the body. We have as example of proteins among others: haemoglobin which allows the transport of oxygen in the blood, and antibodies which protect the body against foreign bodies or to detect and neutralize pathogens in specific way.
There are therefore several scenarios that can arise following a shuffling of chromosomes. An individual can inherit the normal copy of one gene, and the abnormal copy of another, to the point where the abnormal copy is dominant. He can inherit two defective copies of a gene from each of his two parents; he can inherit from a defective copy, and another normal one which compensates for the defects of the defective one. In this case, we say that he is a healthy carrier: he does not develop the disease, but carries an abnormal copy of the gene in the corresponding pair of genes. Since a genetic disease is not always inherited, the genetic anomaly can occur accidentally during the production of gametes (spermatocytes, oocytes) or after the fertilization of an ovum. In this case, it is the descendants of the subject in question or of the healthy carrier who will be affected by the disease. There are also so-called acquired mutations. They are not transferable, and have not been created. The cells concerned can be the cause of cancer. Let us also point out that if in most cases the role of genes is determining in the risk of developing a genetic disease, environmental factors also play a more or less important role because, several such as a poor diet or a poor lifestyle with tobacco consumption for example, can have a negative impact on genetic heritage.
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