HbH vs HbBart

[econdr]

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So the way i understand it, in alpha thalassemia w/ 3 alpha gene mutations, you get HbH, which is a Hb beta tetramer. If you delete all 4 alpha Hb genes, you get Hb Bart, which is Hb gamma tetramer.

Why cant those hydrops babies just produce HbH like the 3 gene deletion if they still have the same beta globin genes intact?

What am I missing here?

 

[RafaTech]

So the way i understand it, in alpha thalassemia w/ 3 alpha gene mutations, you get HbH, which is a Hb beta tetramer. If you delete all 4 alpha Hb genes, you get Hb Bart, which is Hb gamma tetramer.

Why cant those hydrops babies just produce HbH like the 3 gene deletion if they still have the same beta globin genes intact?

What am I missing here?

Babies dont start making Beta chains until after birth. Their hemoglobin is predominantly alpha2-gamma2 chains which have a higher affinity for oxygen to be able to extract O2 from mom's blood.

 

[dude1344]

Im still confused lol...

 

[RafaTech]

Im still confused lol...

Fetal Hb is alpha2-gamma2, when you have alpha-thal with 4 gene deletion there is not enough alpha chains to make a2-g2 hemoglobin, thus 4 gamma chains come together to form HbBart. This is lethal in utero and since beta chains are not formed until birth, there is never the chance to form HbH which is 4 beta chains.

When you have 3 gene deletions in alpha-thal, this is a little more alpha chains around so the baby is able to survive by making some HbF, thus after its born it will start making the beta chains and to replace the gamma chains and you'll get HbH (beta tetramer).

 

[dude1344]

Fetal Hb is alpha2-gamma2, when you have alpha-thal with 4 gene deletion there is not enough alpha chains to make a2-g2 hemoglobin, thus 4 gamma chains come together to form HbBart. This is lethal in utero and since beta chains are not formed until birth, there is never the chance to form HbH which is 4 beta chains.

When you have 3 gene deletions in alpha-thal, this is a little more alpha chains around so the baby is able to survive by making some HbF, thus after its born it will start making the beta chains and to replace the gamma chains and you'll get HbH (beta tetramer).

thanks!

 

[econdr]

Fetal Hb is alpha2-gamma2, when you have alpha-thal with 4 gene deletion there is not enough alpha chains to make a2-g2 hemoglobin, thus 4 gamma chains come together to form HbBart. This is lethal in utero and since beta chains are not formed until birth, there is never the chance to form HbH which is 4 beta chains.

When you have 3 gene deletions in alpha-thal, this is a little more alpha chains around so the baby is able to survive by making some HbF, thus after its born it will start making the beta chains and to replace the gamma chains and you'll get HbH (beta tetramer).

sweet thanks for your response!

 

[WashMe]

Fetal Hb is alpha2-gamma2, when you have alpha-thal with 4 gene deletion there is not enough alpha chains to make a2-g2 hemoglobin, thus 4 gamma chains come together to form HbBart. This is lethal in utero and since beta chains are not formed until birth, there is never the chance to form HbH which is 4 beta chains.

When you have 3 gene deletions in alpha-thal, this is a little more alpha chains around so the baby is able to survive by making some HbF, thus after its born it will start making the beta chains and to replace the gamma chains and you'll get HbH (beta tetramer).

😍 (no homo)