Final answer:
Microtubules in an embryo organize into a mitotic spindle structure during cell division, arranging homologous chromosomes at the metaphase plate. This organization is crucial for the correct separation of chromosomes and genetic diversity. The spindle microtubules attach to chromosomes via kinetochores to orient sister chromatids towards opposite cell poles.
Step-by-step explanation:
The microtubule network in an embryo is intricately arranged to ensure proper cell division and development. During cell division, specifically mitosis or meiosis, microtubules assemble from alpha-tubulin and beta-tubulin monomers. The critical stage where these structures are most visible is during mitotic spindle formation, where microtubules extend from centrioles (in animal cells) or from microtubule organizing centers (MTOCs) in plant cells. These spindle fibers contribute significantly to the arrangement and separation of chromosomes.
In metaphase, homologous chromosomes, paired as tetrads, randomly align at the metaphase plate, and this arrangement is facilitated by the microtubules that maneuver the chromosomes into place. The orientation of each tetrad on the plate is random and independent of others, which is crucial for genetic diversity. As the process transitions to prometaphase, mitotic spindle microtubules continue to develop, engaging in the attachment process through structures called kinetochores on the chromosomes, ensuring that sister chromatids will face opposite poles of the cell.