Diplotene

Diplotene is a substage within the prophase I stage of meiosis, specifically following pachytene. During diplotene, homologous chromosomes, which have undergone synapsis and crossing over during earlier stages, begin to separate slightly. The points where the chromosomes remain connected are known as chiasmata, representing the sites of genetic recombination. The chromosomes appear as pairs of sister chromatids, held together by cohesin proteins, and are visibly distinct. RNA and protein synthesis often resume during diplotene, particularly in oocytes, where the chromosomes may decondense, forming a 'lampbrush' appearance.

Diplotene meaning with examples

• In oocytes, the diplotene stage can last for extended periods, allowing for the accumulation of mRNA and proteins needed for later development. The lampbrush chromosome structure allows for active transcription, essential for oocyte maturation and the eventual formation of an embryo.
• Geneticists analyze chiasmata frequency in diplotene cells to map the relative distances between genes on chromosomes. This helps create genetic maps illustrating the linear arrangement of genes and their recombination frequencies.
• A cell arrested in diplotene may resume meiosis later, indicating a checkpoint controlling developmental progress. This checkpoint, triggered by a hormone surge, facilitates completion of the diplotene stage in female mammals.
• Diplotene chromosomes are visible under a light microscope, providing a useful marker to assess the progression of meiosis in different organisms and identify defects in the synaptonemal complex.
• During the diplotene stage, the cohesion between sister chromatids is crucial for correct chromosome segregation. Disruptions in cohesion can cause aneuploidy, leading to developmental abnormalities.