Sickle Cell Anaemia: Foetal Homozygous Recessive Not Affected

[e-diot]

i've been asked to explain the observation of sickle cell anaemia which is caused by a recessive point mutation in the beta chain of adult haemoglobin, but foetus homozygous recessive is not affected.

why is that? i have been told that foetus has haemoglobin gamma not beta and therefore can't get affected.

i thought that if u had homozygous recessive though, then u would get the disease??

 

[adrenaline]

Sickle cell disease includes the homozygous HBSS but other sickeling syndromes include double heterozygous conditions such as HBS-betathalasemia, HbSC etc.) All of them are associated with structurally abnormal hemoglobin molecule that polymerize under reduced oxygen conditions or dehydration. The fetal hemoglobin F that we are born with does not seem to polymerize as much or is protected from sickeling, but the switch from HBF to HbS occurs after the first few months of life. Some people have a hereditary persistance of fetal hemoglobin (higher concentrations) or have other genetic variants of sickle cell with elevated HbF levels. In general, these patients have mild or minimal disease.

 

[ravenprp]

Sickle cell anaemia is a genetic disorder that is caused by a mutation in the beta chain of adult haemoglobin. This mutation results in the production of abnormal haemoglobin, which causes the red blood cells to become sickle-shaped and less able to carry oxygen. This can lead to a variety of symptoms, including anaemia, pain, and organ damage.

In order for an individual to have sickle cell anaemia, they must inherit two copies of the mutated gene, one from each parent. This is known as being homozygous recessive for the gene. However, in the case of a foetus, this mutation does not always result in sickle cell anaemia.

This is because the foetus produces a different type of haemoglobin, known as haemoglobin gamma, rather than the adult haemoglobin beta. This is because the foetus receives oxygen from the mother's blood through the placenta, and this oxygen needs to be carried by a different type of haemoglobin. Therefore, the mutated beta chain does not affect the foetus in the same way as it would affect an adult with sickle cell anaemia.

It is important to note that even though the foetus does not develop sickle cell anaemia, they still carry the mutated gene. This means that they have the potential to pass on the disorder to their own children if they have a partner who also carries the mutated gene. It is only when both parents are carriers that there is a chance of the child inheriting sickle cell anaemia.

In summary, the reason why a foetus with homozygous recessive sickle cell anaemia does not develop the disorder is because they produce a different type of haemoglobin that is not affected by the mutated beta chain. This highlights the importance of understanding the biology and genetics behind diseases, as it can help us better understand why certain individuals may or may not be affected by them.