**Core Concept:** Karyotyping is a laboratory technique that involves examining the chromosomes of an individual to identify any abnormalities or defects. Major types of chromosome abnormalities include numerical and structural chromosomal anomalies.

**Why the Correct Answer is Right:** Karyotyping can be used to diagnose certain genetic disorders caused by chromosomal abnormalities. One such disorder is Down syndrome (trisomy 21), which is caused by an extra copy of chromosome 21, leading to an increase in the number of chromosomes (numerical abnormality).

**Why Each Wrong Option is Incorrect:**

A. Down syndrome is not caused by a deficiency in any chromosome, making option A incorrect.
B. Karyotyping is used to diagnose chromosomal abnormalities, not deficiencies, making option B incorrect.
C. Karyotyping is not limited to diagnosing only specific genetic disorders like sickle cell anemia (caused by a mutation in one gene), making option C incorrect.
D. Karyotyping is used to diagnose chromosomal abnormalities, not disorders caused by infections or environmental factors, making option D incorrect.

**Clinical Pearl / High-Yield Fact:**

Understanding karyotyping's role in identifying numerical and structural chromosomal abnormalities is essential for medical students, as it helps in diagnosing various genetic disorders like Down syndrome, Klinefelter syndrome, Turner syndrome, and others.

**Correct Answer:** C. Karyotyping can be used to diagnose chromosomal abnormalities, such as Down syndrome (which is caused by trisomy 21), ensuring the correct identification of numerical chromosomal abnormalities.