Resumen de Chaotic egg division causes fall in fertility
Women are reminded only too frequently about biological clocks. Now they actually have a clearer idea of what makes fertility fall--chaotic mix-ups when egg cells divide. Greg Fitzharris at the University of Montreal in Canada and his team have now identified another way in which cells can be left with the wrong number of chromosomes. They have found that eggs from older mice are more likely to behave chaotically during the first phase of dividing than those from young mice. This is caused by microtubules, structures that normally corral chromosomes to opposite ends of a cell before it divides. But in half the cells taken from old mice, microtubules sent chromosomes in different directions causing clumps in three or four spots. This made the resulting egg cells more likely to have the wrong number of chromosomes
