Inherited traits from parents aren't just passed out in random fashion. Inherited traits are passed through the genes of parents to their children. Some traits are passed on only through the mother or only through the father. Others are passed on depending on what traits are strongest between the parents, whether they be dominant traits or just more prevalent within the family. These genes may determine genetic disorders as well.
According to "Keeping It in the Family: Inherited Traits," by Kathryn Williams, people inherit genes from both parents, and what we see are the most dominant genes or sets of genes. Girls have two X chromosomes and boys have an X and a Y. Because the X chromosome is richer in genes than the Y chromosome, females may have twice the opportunity of inheriting a dominant gene than a male. For example, males may inherit hemophilia, a serious blood-clotting disorder, while women are carriers of the gene without having the disorder itself.
While mothers may not exhibit as many recessive traits as fathers, they are easily able to pass these recessive traits on to their children. Because males have one X chromosome and one Y chromosome, any X-linked traits they have must be inherited from the mother, as women only pass on X chromosomes. However, females receive an X chromosome from each parent and may acquire X-linked traits from either parent because of this, according to Kathryn Williams. Pattern baldness and color blindness are thought to be passed on from mothers most often to their sons.
Few traits are passed on only from fathers. A male child, however, receives his maleness from his father, as men pass on a Y chromosome and women do not. In addition, the gene that determines right or left handedness may be passed on from fathers.
Dominant traits can be passed on from either parent. Dominant traits include brown eyes, dimples, curly hair and unattached earlobes, according to Blinn.edu. A parent with brown eyes and a parent with blue eyes may be able to have blue-eyed children if the brown-eyed parent carries the blue-eyed recessive gene as well. However, if the brown-eyed parent only has brown-eyed genes, the chances are very small that their children will have anything but brown eyes. Geneticists use a diagram called a Punnett Square to determine the probability of certain traits being passed on. Athro.com shows examples of different Punnett Squares used.
Recessive traits are also passed on by both parents. Blue and green eyes are both considered recessive traits, but blue is more dominant than green. Albinism and deafness are also recessive traits. Cystic fibrosis, a dangerous inherited disease affecting the mucous membranes of multiple organs, is also carried on a recessive gene. Genetic testing is available to couples trying to conceive to pinpoint the likelihood of genetic disorders in their children.