meiotic drive which is preferential selection during meiosis (germ cell production);
gametic selection which is preferential selection of gametes (germ cells) ; and
postzygotic viability which reflects differences in the ability of conceptions to survive.
All of these mechanisms for selection result in the production of offspring in proportions that deviate from Mendelian predictions. For example, there may be a deficiency of offspring with an autosomal dominant syndrome due to the tendency for it to cause very early pregnancy loss. The proportion of offspring born with the syndrome is less than 50% due to selection.
- Transmission, perinatal
Transmission of a disease-causing agent (a pathogen) from mother to baby during the perinatal period, the period immediately before and after birth. The perinatal period is defined in diverse ways. Depending on the definition, it starts at the 20th to 28th week of gestation and ends 1 to 4 weeks after birth. The perinatally transmitted […]
- Transmission, vertical
Passage of a disease-causing agent (pathogen) from mother to baby during the period immediately before and after birth. Transmission might occur across the placenta, in the breast milk, or through direct contact during or after birth. For example, HIV can be a vertically transmitted pathogen. Also known as perinatal transmission.
- Transmyocardial laser revascularization
A procedure by which a physician uses a laser to make holes in the heart to relieve the pain of severe angina. Transmyocardial laser revascularization has been done from both the outside and inside of the heart. When done from the outside, a laser (carbon dioxide or holmium laser) is placed in proximity to the […]
The grafting of a tissue from one place to another, just as in botany a bud from one plant might be grafted onto the stem of another. The transplanting of tissue can be from one part of the patient to another (autologous transplantation), as in the case of a skin graft using the patient’s own […]
- Transplant, hand and forearm
Transplantation of the hand and the forearm from one person (a deceased donor) to another (the recipient). In the first hand transplant, performed in Ecuador in 1964, the donor hand was rejected after two weeks. The first successful hand and forearm transplant was done in 1998 in Lyon, France. In 1999, surgeons in Louisville, Kentucky, […]