Once together, never apart – isn’t that how the saying goes? Not so in meiosis, the special type of cell division in which gametes, sperm and egg cells are formed. At the start of meiosis the ring-shaped protein complex, referred to as cohesin, is the string that ties the chromosome strands together. The chromosomes are where the blueprint for the body is stored. If each egg cell and each sperm is to come out of meiosis with only one set of chromosomes, these strings need to be cut up in a precise pattern. Scientists from the Max Planck Institute of Biochemistry have demonstrated in baker’s yeast how a kinase enzyme, which is also present in the human body, controls the cleavage of the cohesin rings and coordinates it with the exit from meiosis and gamete formation. It is a mechanism, which could explain how chromosome segregation is regulated, or goes wrong, in human sperm and egg cells.
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