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Chromosomes can only be seen under a microscope when a cell is about to divide.

However, there are times when a person’s genetic code may not be what is expected. “Genetic disorders can happen for many reasons,” explains the Centers for Disease Control and Prevention. “Genetic disorders often are described in terms of the chromosome that contains the gene. If the gene is on one of the first twenty-two pairs of chromosomes, called the autosomes, the genetic disorder is called an autosomal condition. If the gene is on the X chromosome, the disorder is called X-linked.” Previously, Down syndrome and sickle cell anemia were highlighted as common genetic disorders. However, other disorders are caused by mutations in a person’s genetic code. These mutations

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Nicotine and Genetics: The Hereditary Predisposition