Organisms often have more than one chromosomes to carry their genetic materials such as genes. For example, a human individual has 23 pairs of different chromosomes, and a baking yeast Saccharomyces cerevisiae has 16 different chromosomes when in haploid status.
Why do an organism have many chromosomes other than one? Particularly, if one thinks that only genes on chromosomes are useful and the rest may be junk, he may think that putting all genes in a chromosome will be completely fine and this is more efficient in saving energy of synthesizing “useless” portions of chromosomes.
Excitingly, recently two studies published by Shao, et al and Luo, et al demonstrates that reducing the number of chromosomes in the yeast is almostly fine: the yeast with only one chromosome by fusing all the 16 chromosomes grew as well as a wild-type 16-chromosome yeast. Also hybridzing the strains with different chromosome numbers basically produced inviable spores – productive isolation.
These studies also show that the gene expression profiles were not much affected by the number of chromosomes, suggesting that the 3-dimension structure or inter-chromosomal interactions may not be as important as previously thought in gene regulation.
This is really an exciting progress that we can, for the first time, show how an organism with only one chromosome behaves. It also triggers several questions for me:
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What happens if applying the same approach to organisms with larger chromosomes? The total size of the yeast is 12Mb, much smaller than the smallest human chromosome (Y, 57.2Mb).
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Why are single-chromosome organims not observed in nature? This may be related to natural selection process – a slight decrease in growth can have significant effect on the competion of the organism with others in nature.
Look forward to more advances!
Last modified on 2018-08-02