Sickle cells risk being destroyed by the spleen because of their shape and stiffness. The spleen helps filter the blood of infections. Sickle cells get "stuck" in this filter and die. Due to the decreased number of hemoglobin cells circulating in the body, a person with sickle cell is chronically anemic. The spleen also suffers damage from the sickle cells, which block the healthy oxygen-carrying cells.
After repeated blockages, the spleen is very small and does not work properly. Without a functioning spleen, these people are more at risk for infections. Infants and young children are at risk for life-threatening infections. Treatment includes prompt emergency care for fevers and infections, appropriate vaccinations, penicillin, and management of anemia.
Tay-Sachs disease is a fatal disorder in children usually by age 5 that causes a progressive degeneration of the central nervous system. It is caused by the absence of an enzyme called hexosaminidase A or hex A. Without hex A, a fatty substance builds up on the nerve cells in the body, particularly the brain. The process begins early in pregnancy when the baby is developing. It is not apparent until several months after the birth. To date, there is no cure for Tay-Sachs.
Search Encyclopedia. What is autosomal recessive inheritance? In males who have only one X chromosome , an alteration in the only copy of the gene in each cell is sufficient to cause the condition.
In females who have two X chromosomes , one altered copy of the gene usually leads to less severe health problems than those in affected males, or it may cause no signs or symptoms at all. A condition is considered Y-linked if the altered gene that causes the disorder is located on the Y chromosome , one of the two sex chromosomes in each of a male's cells.
Because only males have a Y chromosome, in Y-linked inheritance, a variant can only be passed from father to son. Y chromosome infertility , some cases of Swyer syndrome. In codominant inheritance , two different versions alleles of a gene are expressed, and each version makes a slightly different protein.
Both alleles influence the genetic trait or determine the characteristics of the genetic condition. ABO blood group, alpha-1 antitrypsin deficiency. Mitochondrial inheritance , also known as maternal inheritance, applies to genes in mitochondrial DNA.
Mitochondria, which are structures in each cell that convert molecules into energy, each contain a small amount of DNA. Because only egg cells contribute mitochondria to the developing embryo, only females can pass on mitochondrial variants to their children. Conditions resulting from variants in mitochondrial DNA can appear in every generation of a family and can affect both males and females, but fathers do not pass these disorders to their daughters or sons.
Leber hereditary optic neuropathy LHON. Many health conditions are caused by the combined effects of multiple genes described as polygenic or by interactions between genes and the environment. Such disorders usually do not follow the patterns of inheritance listed above. For more information, please see What are complex or multifactorial disorders? Disorders caused by changes in the number or structure of chromosomes also do not follow the straightforward patterns of inheritance listed above.
To read about how chromosomal conditions occur, please see Are chromosomal disorders inherited? Other genetic factors sometimes influence how a disorder is inherited. For an example, please see What are genomic imprinting and uniparental disomy? To provide you with the most relevant and helpful information and to understand which information is beneficial, we may combine your e-mail and website usage information with other information we have about you.
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