Final answer:
The γ-tubulin ring complex serves as the template for the assembly of the first row of tubulin dimers in the pericentriolar materials of the centrosome, which is vital for microtubule organization and cell division.
Step-by-step explanation:
In the pericentriolar materials (PCM) of the centrosome, the template on which the first row of tubulin dimers assemble is known as a γ-tubulin ring complex (γ-TuRC). This complex serves as a nucleation site for the polymerization of α-tubulin and β-tubulin into microtubules. The centrosome, a critical microtubule-organizing center located near the nucleus of animal cells, contains a pair of centrioles, which are cylinders composed of nine triplets of microtubules, held together by non-tubulin proteins. During cell division, the centrosome plays a fundamental role in organizing the mitotic spindle, which is essential for the segregation of chromosomes into two new cells.