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How do mitotic divisions preserve the chromosome number in blastomeres?
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Animal development
The embryos of many animals appear similar to one another in the earliest stages of development and progress into their specialized forms in later stages.
During animal development, the process of cleavage involves a series of consecutive mitotic divisions that transform the zygote into a multicellular organism. These divisions preserve the chromosome number in blastomeres through the following mechanism:1
- Chromosome Replication: Before each division, the chromosomes within the nucleus, which carry the organism's genetic information, undergo duplication. This requires the synthesis of DNA.1
- Equal Distribution: During mitosis, each replicated chromosome splits into two daughter chromosomes. The spindle fibers pull these chromatids to opposite ends of the cell, ensuring that each of the two resulting daughter blastomeres receives an identical and complete diploid set of chromosomes.12
Because each blastomere receives the full complement of paternal and maternal chromosomes, the genetic integrity of the developing organism is maintained throughout the cleavage period.3