Research in Progress

Miscellaneous

Meiotic Expansion Mutations

DNA analysis of cells from the testes of two men who died from HD reveals that trinucleotide repeat (TNR) expansions (please see The Basics of Huntington’s Disease, Part 2), were present before the end of the first stage of meiosis. Meiosis is a two-part process of cell division, resulting in the production of the male and female gametes (sperm and egg). Some mutations were perhaps present before meiosis began, but the largest HD mutations were found in cells that had already undergone meiosis, indicating that mutations may continue to appear during or after this cell-division process. Scientists originally believed that expansion occurs during mitosis, another cell-division process that results in the production of body cells, but there is now evidence that expansion occurs before the end of meiosis, or even during the last stages of sperm maturation (please see All About Mutations, Part 13).

In the past, studies of the expansion mutations in spermatogonia (precursor to sperm cells) suggested that the mutation process occurred after meiosis (in other words, during mitosis), mediated by two processes that may cause the genes to rearrange or become unstable, which results in many diseases, including HD. However, scientists have recently observed mutations in spermatogonia that occur during meiosis.

To learn more about meiotic expansion mutations, please click here.

Last Modified: 5-10-04

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