For karyotyping, the dividing cells are arrested by the addition of colchicines in the following mitotic phase
**Core Concept**
Colchicine is a microtubule-disrupting agent used to arrest cell division in a specific phase, allowing for the analysis of chromosomes in the resulting metaphase plate. This process is crucial for karyotyping, which is the study of the number and structure of chromosomes in an individual's cells.
**Why the Correct Answer is Right**
Colchicine works by binding to tubulin, a protein that makes up microtubules, which are essential for the separation of chromosomes during cell division. By inhibiting microtubule formation, colchicine causes the cell to arrest in metaphase, where the chromosomes are condensed and aligned at the metaphase plate. This allows for the accurate analysis of chromosome number and structure.
**Why Each Wrong Option is Incorrect**
**Option A:** Prophase is the stage where chromosomes condense and the nuclear envelope begins to break down, but colchicine does not specifically target this phase.
**Option B:** Anaphase is the stage where sister chromatids are separated and moved to opposite poles of the cell, but colchicine prevents this separation.
**Option C:** Telophase is the stage where nuclear envelopes begin to reform around each set of chromosomes, but colchicine's effect is seen earlier in the cell cycle.
**Clinical Pearl / High-Yield Fact**
Colchicine is used not only in karyotyping but also in the treatment of gout, where it reduces inflammation by inhibiting the migration of neutrophils.
**Correct Answer: B. Metaphase**