---
title: OB/GYN
---

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# D is the correct answer

Explanation:

 

**Adult hemoglobin** consists of two pairs of globin polypeptide chains: one pair of alpha and one pair of non-alpha chains, each of which has an attached heme molecule. **Alpha-thalassemia** is caused by a deletion of two or more copies of the four alpha-globin genes. Women with deletions of both alpha-globin genes on one chromosome (**αα**/**--**) are at risk of having a fetus with alpha-thalassemia major, while the absence of alpha-globin genes (--/--) is associated with hydrops fetalis, intrauterine death, and preeclampsia.

![](https://roshreview.imgix.net/36555dbc507b67470e8b64bf6b6d3902_Image%20-%20Alpha%20Thalassemia%20%408x.png?w=4000&fit=max&q=30&auto=compress)

Deletion of one alpha-globin gene (**α-**/**αα**) **(C)** is an asymptomatic condition and clinically unrecognizable from the normal genotype. Deletion of two globin genes, alpha-thalassemia minor, causes mild microcytic anemia and is common among individuals of Southeast Asian, African, and West Indian descent. In individuals of African descent, alpha-thalassemia minor is usually due to a deletion of a single alpha-globin gene on each chromosome (**α-**/**α-**) **(B)**, which rarely results in fetuses affected by alpha-thalassemia major. This is in contrast to the common Asian genotype (αα/--). Deletion of three alpha-globin genes (**α-**/**--**) **(A)**, hemoglobin H disease, is associated with more severe microcytic and hemolytic anemia and can also result in a fetus with alpha-thalassemia major.

  

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