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Meaning of Genotype
Genotype is the genetic makeup of an individual with reference to a trait or multiple traits. They are the collection of genes passed from parents to the children. Alleles or Allelomorphs are also referred to as the genes. Children born of a parent will have a different genotype. Exceptions are seen in cases of twins or multiple births that are fertilized from the same egg. Human beings have two alleles with each pair inherited from each parent. An allele represents a gene.
Before the advent of modern medicine (read about how modern medicine came to Nigeria here), there was high mortality and infant death rates. All these children lost to the cold hands of death were referred to as “abikus”. All these happened because there was no knowledge of blood group or genotype. People that get married irrespective of their genetic makeup should not be blamed for their ignorance. But with the advent of modern medicine( read about modern medicine and its advantages ), biological explanations are now being made on the causes of infant death rate, this led to the discovery of sickle cells in Africa, especially in Nigeria. Before marriage, partners should be aware of their genotypes and blood group as the society no longer provides an excuse for this ignorance (read an interesting article on no excuse for ignorance here). Parents should check the genotype of their children during pregnancy or immediately after birth. This will help to know the health status of the child and what they have to do to sustain and maintain the child’s health. (Read an interesting article on how a child’s blood group is formed from the parent’s blood here)
There are four genotypes in humans – AA, AS, SS and AC. AC genotype is not so common and popular unlike the other three. SS and AC are the abnormal genotypes or the sickle cells. The knowledge of genotype is important when choosing life partners. Intending couples should know both their own genotype as well as their partner’s genotype at the early stage of their relationship before they are well rooted in love and emotions. Emotions and time spent in the relationship can cloud people’s judgment or decision to break up if they are not compatible, thus, giving birth to sickle cell children and subjecting themselves and their children to pain, torture, and agony.
Possible Outcomes of Different Genetic Combination
AA + AA = AA, AA, AA, AA
AA + AS = AA, AS, AA, AS
AA + SS = AS, AS, AS, AS
AA + AC = AA, AA, AA, AC
AS + AS = AA, AS, AS, SS
AS + SS = AS, SS, SS, SS
AS + AC = AA, AC, AS,SS
SS + SS = SS, SS, SS, SS
AC + SS = AS, AS, SS, SS
AC + AC = AA, AC, AC, SS
People with the genotype AA are prone to malaria sickness (Read about why people with genotype AA are prone to malaria here) at their early ages. Sickle cell arises when there is any blockage in the blood vessels which inhibits the flow of oxygen. When the red blood cell does not have the required oxygen, there will be changes in its original shape (disc shape) to a “Sickle-like” or “crescent-like shape”, Thus, the name “sickle cell”. Sickle cell patients experience severe pains in body parts that lack oxygen flow. Their bone marrows will fail to produce red blood cells and this result in anemia. To save this crisis, blood is usually transfused to them.
In terms of compatibility, someone with an AA genotype can marry anybody. It is safe for someone with AS to marry someone with AA genotype. The combinations of AS and AS, AS and AC should not be risked. There is a probability of having an SS. Although. Two sickle cells should not even have a relationship or get married. Individuals with the AA genotype should help you prevent genetic abnormalities by marrying the AS, AC, and SS. By this, we are hopeful to eradicate sickle cells in the world.
Blood Groups / Blood Types
The red blood cells that transport oxygen in the body carries two antigens, which are the A and B antigens. These antigens determine the blood group. Blood groups are represented with A, AB, O, and B. When the red blood cell carries only the A antigen, the blood group is ‘A’, it is ‘B’ when the blood cell has only the B antigen. When both A and B antigens are present, the blood group is ‘AB’. Finally, when there is neither A nor B antigen, the blood group is referred to as ’O’.
Below is the crossbreed of different blood groups and the products (offsprings)
A + A = A or O
B + B = B or O
A + B = A, B, AB or O
A + O = A or O
B + O = B or O
A + AB = A, B or AB
O + O = O only
The genotype of blood type A is AA or AO. The antigens on the blood cell are A and antibodies in the blood plasma are B.
For blood type B, the genotype is BB or BO with B as the antigens and B as antibodies.
The blood type AB (also known as universal blood recipients and rarest blood type) has the genotype to be AB. The antigens are both A & B, and no antibodies in the blood plasma.
The blood type O (also known as universal blood donors) has the genotype to be OO. There are no antigens but has antibodies to be A or B.
Rhesus factor or the ‘D’ antigen is also found on the surface of the red blood cell. Those with it are seen to be “rhesus positive or Rh+” and those without are “rhesus negative or Rh-“. There is a possibility of having both Rh + and Rh -. A person who is Rh + will produce antibodies against Rh – blood cells. A patient with Rh + can receive blood from someone who is Rh + or Rh -. But an Rh – can only receive blood from Rh -.
Knowing your blood type is important during pregnancy. If the mother is Rh- and the father is Rh +, the fetus can either inherit the Rhesus gene from either the father or mother. Complications (Rh incompatibility) occur when the Rhesus factor of the fetus contradicts that of the mother. This is common when a pregnant woman has Rh – and the fetus has Rh+. If the blood of the Rh + baby mixes with the mother’s, it can lead to the production of antibodies against the baby’s blood known as Rh-sensitization. To curb this disease, pregnant women should always meet regularly with obstetricians and human anti-D immune globulin or immunoglobulin should be administered to those with the complications.
*O are universal blood donors (donate blood to all blood types).
*AB+ are universal blood recipients (receive from all blood types).
*A+ can receive blood from A+, A-, O+ & O-
* A- from A- & O-
*B+ from B+, B-, O+ & O-
*B- from B- & O-
*AB- from A-, B-, AB- & O-
* O+ from O+ & O-
*O- from O-
The importance of knowing one’s blood group and genotype before marriage cannot be overemphasized. It determines the donor and recipient of blood transfusion and also helps in determining paternity. A person with one blood type or group can produce antibodies against the other. For instance, a person with blood type A makes antibodies against blood type B. If this person is given blood of type B, his or her type antibodies will bind to the antigens on the type B blood cells cause the blood to clump together. Compatibility of blood type is necessary before transfusing blood in times of accidents and emergencies.
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