What is a Genotype?
By Nelson Gozah
A genotype can simply be referred to as, the genetic makeup of an individual or group of people with reference to a single trait, set of traits, or an entire complex of traits. In a nutshell: your genotype is your complete heritable genetic identity; the sum total of genes transmitted from parent to offspring.
There are four hemoglobin genotype in humans:
AA, AS, SS and AC (uncommon). SS and AC are the abnormal genotypes or the sickle cells and AA and AS are normal and carrier genotype respectively. This means a normal genotype has a normal shape hemoglobin which is biconcave while the abnormal genotype has an abnormal shape of hemoglobin which is roughen and sickle in shape. We all have a specific pair of these hemoglobin in our blood which we inherited from both parents.
What then is A Sickle Cell?
Sickle cell disease (SCD) is a genetic disorder resulting from the presence of a mutated form of hemoglobin. The most common form of SCD is homozygous HbS disease (HbSS), an autosomal recessive disorder first described by Herrick in 1910. SCD causes significant morbidity and mortality, particularly in people of African and Mediterranean ancestry .
Morbidity, frequency of crisis, degree of anemia, and the organ systems involved vary considerably from individual to individual.
In other words, Sickle cell disease can also be described as a type of hereditary disorder in which there aren’t enough healthy red blood cells to carry oxygen throughout the body. Normally, the flexible, round red blood cells move easily through blood vessels. In sickle cell disease, the red blood are shaped like sickles or crescent moons. These rigid, sticky cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.
There’s no definite cure for sickle cell disease. But treatments can relieve pain and help prevent complications associated with the disease.
Signs and Symptoms
Signs and symptoms of sickle cell anemia usually appear around 5 months of age. They vary from person to person and change over time. Signs and symptoms can include:
1. Anemia.
Sickle cells break apart easily and die, leaving you with too few red blood cells. Red blood cells usually live for about 120 days before they need to be replaced. But sickle cells usually die in 10 to 20 days, leaving a shortage of red blood cells (anemia).
Without enough red blood cells, your body can’t get enough oxygen, causing fatigue.
2. Episodes of pain.
Periodic episodes of pain, called pain crises, are a major symptom of sickle cell disease. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels to your chest, abdomen and joints. Pain can also occur in your bones.The pain varies in intensity and can last for a few hours to a few weeks. Some people have only a few pain crises a year. Others have a dozen or more pain crises a year. A severe pain crisis requires a hospitalization.
Some adolescents and adults with sickle cell disease also have chronic pain, which can result from bone and joint damage, ulcers, and others.
3. Swelling of hands and feet.
The swelling is caused by sickle-shaped red blood cells blocking blood flow to the hands and feet.
4. Frequent infections.
Sickle cells can damage your spleen, leaving you more vulnerable to infections.
Now, why is it Important to Know Your Genotype?
I believe, by now you would have a glimpse of why you need to know your sickling status. Knowing one’s hemoglobin genotype or sickling status before choosing a life partner is important because there may be compatibility issues which could have negative effects when it comes to conception. Thus, knowing your sickling status, would help you make an informed choice on which partner with what genotype you should marry and conceive with. Below, is a short list of the genotypes that are compatible and incompatible;
✓ Genotype AA can marry AA, AS or SS because there no or less probability of conceiving an SS child.
✓ Genotype AS is better off with AA but too risky with AS and SS i.e AS and AS, AS and AC are too risky and therefore not medically recommended since there a fifty percent chance of conceiving an SS child(in the case of AS and AS).
✓ Two sickle cells thus genotype SS and SS should strictly avoid conception, since there is a hundred percent likelihood of couples conceiving an SS child.
With this, it is crystal clear that conception between incompatible genotypes would end up in bringing up a sickle cell child. Hence, it would be very prudent for couples to know their sickling status prior to marriage and conception.
Thank You.
Your contributions on this topic is always welcomed.
REFERENCE :
Professional Guide To Diseases by Lippcott Williams & Wilkins
www.mayoclinic.org