Naming inversion types: When an inverted chromosomal segment includes the centromere, what is this inversion called?

Introduction / Context:
Inversions are structural rearrangements that reverse a chromosome segment. Correctly naming them based on whether the centromere is within the inverted block is essential for predicting meiotic outcomes and cytogenetic behavior.

Given Data / Assumptions:

• A chromosome harbors an inversion.
• The inverted segment explicitly includes the centromere.

Concept / Approach:
A pericentric inversion includes the centromere; a paracentric inversion does not. This distinction determines whether crossovers produce duplication/deletion chromatids (pericentric) or dicentric/acentric products (paracentric). Naming conventions are universal in cytogenetics for clarity in clinical and research contexts.

Step-by-Step Solution:

Verification / Alternative check:
Standard cytogenetic atlases define these terms identically, aligning with observed meiotic segregation patterns.

Why Other Options Are Wrong:

• Paracentric: excludes the centromere.
• Double/inverted inversion: not standard nomenclature here.
• Isochromosome: a different abnormality involving mirror-image arms, not an inversion.

Common Pitfalls:
Confusing the outcomes of crossovers for paracentric versus pericentric inversions and then misnaming the inversion type.

Final Answer:
Pericentric inversion