Multiple Allele Inheritance (Blood Types)

Multiple Allele Inheritance: There are more than two alleles for a trait. Organisms still only inherit two of them, but there is a greater variety of genotypes and phenotypes.

Example: Rabbit coats.

Giant Rabbits

ABO Blood groups The result of Multiple allele inheritance (as well as complete dominance).

A History of Transfusions Blood transfusion is the process of transferring blood or blood-based products from one person into the circulatory system of another. Blood transfusions can be life-saving in some situations, such as massive blood loss due to trauma, or can be used to replace blood lost during surgery. Blood transfusions may also be used to treat a severe anaemia or conditions caused by blood diseases.

1818, Dr. James Blundell Dr. James Blundell, a British obstetrician, first experimented with blood transfusions in dogs, and completed his first successful human transfusion in 1818. He completed four successful transfusions out of slightly more than twice this number.

Blundell’s first successful transfusion of human blood was for the treatment of postpartum hemorrhage. He used the patient's husband as a donor, and extracted four ounces of blood from his arm to transfuse into his wife.

Karl Landsteiner (early 1900s) In 1909, Landsteiner classified the blood of human beings into the now well-known A, B, AB, and O groups and showed that transfusions between individuals of groups A or B do not result in the destruction of new blood cells and that this catastrophe occurs only when a person is transfused with the blood of a person belonging to a different group. (He had suggested that, because the characteristics which determine the blood groups are inherited, the blood groups may be used to decide instances of doubtful paternity.)

Dr. Richard Lewisohn, (1915) Dr. Richard Lewisohn, at New York's Mount Sinai Hospital, formulates the optimum concentration of sodium citrate that can be mixed with donor blood to prevent coagulation, but pose no danger to the recipient -- .2 percent. (Isotonic to blood)

Agglutination If you are given the wrong blood type, agglutination can occur, which may result in clumping of cells. This may result in death.

Testing for Blood Types Add a drop of anti-A antibodies (left) to blood drop A Add drop of anti-B antibodies (right) to blood drop B See If Drop A and Drop B Are Clumped By Antibodies [Phenotype Percentages Based On U.S. Population]

Type O (45%): No clumping in blood drops A or B

Type A (42%): Clumping in blood drop A with anti-A antibodies

Type B (10%): Clumping in blood drop B with anti-B antibodies

Type AB (3%): Clumping in both blood drops A and B

The Rh factor The Rh factor makes blood positive or negative.

Rh factor The Rh blood group is determined by a single gene with two alleles positive and negative. Rh stands for “Rhesus factor” because it was discovered in rhesus monkeys. The positive allele Rh+ is dominant, so persons who are Rh+ Rh+, or Rh+ Rh-, both have positive Rh factors. Individuals with Rh- Rh- alleles negative.

Rh incompatibility Rh incompatibility occurs when the mother's blood type is Rh negative and her fetus's blood type is Rh positive. An alternative name is Rh disease. If a pregnant woman is Rh negative and the baby's father is Rh positive, then the baby may inherit the father's blood type, creating incompatibility between the mother and the fetus.

With Rh incompatibility, if some of the fetal blood gets into the mother’s blood stream, and her body will produce antibodies. These antibodies could pass back through the placenta and harm the developing baby's red blood cells, causing very mild to very serious anemia in the fetus. The first baby is usually safe, because fetal and maternal blood usually do not mix until delivery.

If the second baby is also Rh positive, there's a risk that the mother’s antibodies will attack the baby’s blood cells and cause problems.

Treatments Rh disease is rare today, because mothers who are Rh negative receive injections with a drug called Rhogam. Rhogam removes Rh positive fetal cells from the mother's blood stream before her body recognizes them and begins making antibodies. All mothers who are Rh negative receive a shot of Rhogam at 28 weeks. (If antibodies are present and anemia is detected in the fetus, a blood transfusion is performed to replace the fetus's blood supply with Rh-negative blood, which will not be damaged by antibodies the mother’s immune system has created.)