**Core Concept**
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a congenital disorder characterized by thymic aplasia, parathyroid gland absence or hypoplasia, and associated with immunodeficiency and congenital heart defects. This condition is caused by a deletion in chromosome 22q11.2.

**Why the Correct Answer is Right**
The deletion in chromosome 22q11.2 leads to the absence or hypoplasia of the parathyroid glands, resulting in hypocalcemia due to insufficient parathyroid hormone (PTH) production. Thymic aplasia impairs T-cell development and maturation, leading to immunodeficiency. Congenital heart defects, such as outflow tract anomalies, are also common in DiGeorge syndrome. The absence of parathyroid glands and thymus is due to the failure of the third and fourth pharyngeal pouches to develop properly.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the features of DiGeorge syndrome. While Turner syndrome does involve heart defects, it is not associated with thymic aplasia or parathyroid gland absence.
**Option B:** This option is incorrect because it does not accurately describe the features of DiGeorge syndrome. While Trisomy 21 (Down syndrome) involves heart defects, it is not associated with thymic aplasia or parathyroid gland absence.
**Option C:** This option is incorrect because it does not accurately describe the features of DiGeorge syndrome. While Noonan syndrome involves heart defects, it is not associated with thymic aplasia or parathyroid gland absence.

**Clinical Pearl / High-Yield Fact**
DiGeorge syndrome is often associated with other congenital anomalies, including cleft palate, cardiac anomalies, and renal abnormalities. It is essential for clinicians to recognize the characteristic features of this syndrome to provide timely diagnosis and management.

**Correct Answer:** C.