Individuals who seek genetic testing are usually searching for something specific. The most common goals are to establish familial relationships or to search for the genetic markers of a disease. In such situations, whole families frequently have the testing done and compare results, and it can be puzzling when the results differ from one family member to another. To understand genetic evaluation results, it is first necessary to comprehend just a bit of genetics.
Most cells in the human body contain 23 pairs of chromosomes. Twenty-two of those pairs, which are sometimes called autosomes, look the same in women and men.
When a child is formed, 23 chromosomes are inherited from the father, and 23 are inherited from the mother. The sex chromosome in the mother is always an X. The mother has a pair of X chromosomes, and her contribution to this kid will be an X chromosome no matter which one is given. This is the reason doctors say that the gender of the child is determined by the father. If he provides an X chromosome, then the child’s 23rd chromosome is going to be an X-X pair and the child will be a girl. If he supplies a Y, then the child will have an X-Y pair for the sex chromosome and is going to be a boy.
The other chromosomes may seem alike, but on a molecular scale they’re not. Approximately 24,000 genes are contained on the 23 pairs of chromosomes. As a child’s sex is determined by the specific sex chromosome he or she receives from the father, other traits are dependent on the specific genes passed down on every chromosome. Siblings may have very similar outward looks, but the specific gene combinations on the chromosomes can cause very different test results.
Occasionally a single gene is sufficient to cause expression of a certain trait or illness. When this is true, the inheritance is said to be autosomal dominant. Sometimes the same gene must be inherited from both the mother and the father for saying to occur. When this occurs, the inheritance is believed to be autosomal recessive.
The situation is further complicated in that not all genes really express. Some genes are simply markers or switches that turn other genes on or off. Siblings might both receive a receptor, or a set of genes, for an expression that is either autosomal dominant or recessive, but not receive the genetic change or switches that turn the gene on.
With everybody made up of the plethora of gene combinations, not just from their parents, but also grand-parents, great grand-parents and so-forth back family generations, it’s easy to see why same family members genetic tests may lead to different outcomes. This is why it’s a good idea to get several family members tested across different generations so that you can discover a stronger connection to your family’s ancestry history. It is also very exciting to discover new and wonderful things about yourself and your family connections to it’s past.