1. Cell Biology
  2. Chromosomes and Gene Expression
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Meiosis: Helping chromosomes and chromatids stay on track

  1. Soni Lacefield  Is a corresponding author
  1. Indiana University, United States
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Cite this article as: eLife 2012;1:e00386 doi: 10.7554/eLife.00386
2 figures

Figures

The different stages of meiosis. In this illustration the cell has two chromosomes (shown here in yellow and blue in the leftmost cell) before meiosis starts. These chromosomes are replicated to produce sister chromatids that are held together by cohesins (grey circles around the sister chromatids). During the next stage of meiosis, called Prophase I, chromosomes with similar sequences form pairs and undergo recombination, creating physical links that hold the homologs together. Next, during metaphase I, the sister kinetochores (black circles) are clamped together by a protein complex called monopolin, and the spindle microtubules (purple) attach homologous chromosomes to spindle poles (also purple) at opposite ends of the cell. Homologous chromosomes then segregate during anaphase I. During metaphase II, sister chromatids attach to opposite spindle poles and separate in anaphase II, creating meiotic products with half the set of chromosomes.

Proper timing of the interactions between spindle microtubules and kinetochores is essential for meiosis to proceed correctly. During metaphase I in normal meiosis (top), homologous chromosomes become attached to opposite spindle poles by spindle microtubules, and are then segregated in anaphase I (as shown in Figure 1). However, if the microtubules attach to the kinetochores prematurely (bottom), sister chromatids will be segregated in meiosis I, which can ultimately lead to miscarriage or birth defects in babies.

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