Have you ever been asked “What’s your genotype?” It’s a common question for partners seeking to get married, children seeking to enroll into a school, or individuals looking for a job. Doctors too may ask about your genotype when you go for a checkup or treatment. So what’s genotype and how does it work?
What’s a genotype
Genotype refers to an individual’s genetic makeup. It is an entire library of genes that determines height, eye colour, blood group, susceptibility to some diseases, and even the ability to roll one's tongue.
These traits are contained in units called genes. The traits exist in multiple forms or alleles. The alleles may be identical (homozygous) or different (heterozygous). The genes and alleles are packed tightly into larger units known as chromosomes. We inherit our genes from our parents, one copy from dad and one copy from mum, and they combine to create our unique genotypes.
What's blood genotype?
Blood genotype refers to the genetic makeup of our blood components. It is used interchangeably with haemoglobin genotype (Hb genotype), which refers to the genes that code for haemoglobin. Haemoglobin is a protein in red blood cells that carries oxygen from the lungs to tissues.
An average adult has the HbA genotype, which produces HbA with two normal globins. A change or mutation in the normal Hb genotype produces abnormal haemoglobins, such as HbS and HbC, which may affect red cell functions.
There are several different genotypes:
- AA: normal haemoglobin genotype
- AS: sickle cell trait
- AC: haemoglobin disease
- SS: sickle cell anaemia
- SC: sickle cell disease
How is the blood genotype inherited?
Like all genotypes, the Hb genotype is inherited from both parents. The two copies of the Hb genes from your parents combine to determine the type of haemoglobin your red cells produce.
Haemoglobin has two components: the haem component and the globin component. You can guess this from the name: haem + globin = haemoglobin. The Hb genotype codes for the globin component, which may be an alpha globin or a beta globin.
Why is the blood genotype important?
Blood genotypes play a significant role in determining the risk of developing certain diseases. For instance, an individual with the HbAA genotype is more likely to have malaria, while someone with the HbSS genotype is more vulnerable to infections.
Here is why. Malaria parasites survive better in red blood cells with normal haemoglobin than in sickled red cells. Individuals with sickle cell anaemia are likely to have infections because their immune system is weakened by damages caused by sickled red cells.
Other importance of blood genotype include:
- Improved family planning
Testing for blood genotype can help you plan your family and ensure that your children are born healthy and without avoidable genetic disorders.
- Inherited diseases
With a genotype test, you can know your risk for certain inherited diseases and know how to manage them proactively.
- Personalised medicine
Knowing your genotype can also help develop personalised medicine. This type of medicine is tailored to the individual and considers their unique genetic makeup.
How to check your blood genotype
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Blood genotype is often tested using the haemoglobin electrophoresis method. This method separates the blood based on the type of haemoglobin molecules present. The molecules spread out as bands on special paper, and the bands are compared with standard haemoglobin bands to identify abnormal ones like HbS or HbC.
A scientist will collect a small volume of blood from you for the test, which usually lasts a few minutes to an hour. The results are usually ready in hours or days.
It is important to check your blood genotype at a registered and reliable laboratory, or at different laboratories to ensure the accuracy of your results. There have been few reported cases of error in blood genotype testing.
Genotype compatibility for marriage
Knowing one’s genotype is essential for a happy marriage, particularly where hereditary diseases such as sickle cell disease are common. Genotype compatibility describes how well the genes for particular traits match.
Parents who have incompatible genotypes, such AS and SS or AS and AS, run the risk of passing on sickle cell disease to their offspring. To avoid these consequences, couples should get genetic testing done before getting married.
Here is a table illustrating genotype compatibility for marriage:
Parent Genotype | Offsprings | Compatibility |
|---|---|---|
AA + AA | AA, AA, AA, AA | Compatible (Excellent) |
AA + AS | AA, AS, AA, AS | Compatible (Good) |
AA + SS | AS, AS, AS, AS | Compatible (Fair) |
AA + SC | AS, AC, AS, AC | Compatible (Fair) |
AA + AC | AA, AA, AA, AC | Compatible (Good) |
AS + AS | AA, AS, AS, SS | Incompatible (very bad) |
AA + CC | AC, AC, AC, AC | Compatible (Good) |
AS + SS | AS, SS, SS, SS | Incompatible (very bad) |
AS + AC | AA, AC, AS, SC/SS | Incompatible (very bad) |
AS + SC | AS, AC, SS, SC | Incompatible (very bad) |
SS + SS | SS, SS, SS, SS, | Incompatible (very bad) |
SS + SC | SS, SC, SS, SC | Incompatible (very bad) |
AC + SS | AS, AS, SS, SS | Incompatible (very bad) |
SS + AC | AS, SC, AS, SC | Incompatible (very bad) |
AC + AC | AA, AC, AC, SS/CC | Incompatible (very bad) |
SS + CC | SC, SC, SC, SC | Incompatible (very bad) |
SC + AC | AS, SC, AC, CC | Incompatible (very bad) |
AC + CC | AC, AC, CC, CC | Incompatible (very bad) |
SC + SC | SS, SC, SC, CC | Incompatible (very bad) |
Notes:
- Compatible (Excellent): No risk of genetic disorders
- Compatible (Good): Low risk of genetic disorders
- Compatible (Fair): Moderate risk of genetic disorders
- Incompatible (Very Bad): High risk of genetic disorders
Conclusion
The blood is more than just a means of transporting oxygen and nutrients within the body. Understanding your blood genotype is a powerful way to take charge of your health, avoiding potentially life-threatening disorders, and even finding compatible partners.
