Individuals who seek genetic testing are often searching for something specific. The most common goals are to establish familial relationships or to look for the genetic markers of a disease. In these situations, whole families often have the testing done and compare results, and it can be puzzling when the results differ from one relative to another. To understand genetic evaluation results, it is first necessary to comprehend only a bit of genetics.
Twenty-two of the pairs, which are sometimes called autosomes, look the same in men and women.
The sex chromosome from the mother is always an X. The mother has a pair of X chromosomes, and her contribution to the child will be an X chromosome no matter which one is given. This is why doctors say that the sex of the child is determined by the father. If he provides an X chromosome, then the child’s 23rd chromosome will be an X-X pair and the child will be a girl. If he provides a Y, then the child will have an X-Y set for the sex chromosome and will be a boy.
Another chromosomes may seem alike, but on a molecular scale they’re not. Approximately 24,000 genes are contained on the 23 pairs of chromosomes. Just as a child’s sex is determined by the particular sex chromosome he or she receives from the father, other traits are dependent on the specific genes passed down on each chromosome. Siblings may have quite similar external looks, but the specific gene combinations on the chromosomes can lead to very different evaluation results.
Sometimes a single gene is sufficient to cause expression of a particular trait or illness. When this is true, the inheritance is thought to be autosomal dominant. Sometimes the same gene must be inherited from both the mother and the father for expression to occur. When this occurs, the inheritance is said 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 gene, or a set of genes, to get an expression that is either autosomal dominant or recessive, but not receive the genetic change or switches which turn the gene on.
With everybody made up of the abundance of gene combinations, not only 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 you can discover a stronger link to your family’s ancestry history. Additionally it is very exciting to discover new and terrific things about yourself and your family relations to it is past.