Chromosome number changes in yeast

Jul 21, 2011

Researchers from Trinity College Dublin have uncovered the evolutionary mechanisms that have caused increases or decreases in the numbers of chromosomes in a group of yeast species during the last 100-150 million years. The study, to be published on July 21st in the open-access journal PLoS Genetics, offers an unprecedented view of chromosome complement (chromosome number) changes in a large group of related species.

A few specific cases of chromosome number changes have been studied in plants and animals, for example the fusion of two chromosomes that gave rise to chromosome 2 in humans, giving humans a chromosome count of 23 pairs compared to 24 pairs in great apes. The family of yeasts studied in this new research spans a similar evolutionary distance to that of vertebrates. The availability of completely sequenced genomes facilitated the reconstruction of ancestral genome structures at different evolutionary time points. Tracing the positions of essential parts of chromosomes (centromeres and ) through time allowed for the identification of specific genome rearrangement events that resulted in chromosome complement changes.

The addition of large numbers of genes is not often tolerated by cells, and neither are deletions of large numbers of genes. This restricts the types of possible changes in chromosome complement to rearrangements of genes on chromosomes that maintain the same number of genes.

The researchers show that, in yeasts, chromosome complement has decreased in all except one notable event, a whole genome duplication – an event that doubled the complement of an ancestor of several of the species from 8 chromosomes to 16. The decreases in chromosome number were mostly by the fusion of whole , similar to the one that gave rise to chromosome 2 in humans. One exception to this mechanism was the breakage of a chromosome and the subsequent fusion of the two broken edges to two different chromosome ends.

Although some aspects of the research are specific to yeast, many of the mechanisms of chromosome number change in are similar to those found in other organisms and therefore shed light on how chromosome complements evolve.

Explore further: The origin of the language of life

More information: Gordon JL, Byrne KP, Wolfe KH (2011) Mechanisms of Chromosome Number Evolution in Yeast. PLoS Genet 7(7): e1002190. doi:10.1371/ journal.pgen.1002190

Related Stories

Hotspots found for chromosome gene swapping

Nov 29, 2007

Crossovers and double-strand DNA breaks do not occur randomly on yeast chromosomes during meiosis, but are greatly influenced by the proximity of the chromosome’s telomere, according to research in the laboratory of Whitehead ...

Chromosome imbalances lead to predictable plant defects

Nov 03, 2010

Physical defects in plants can be predicted based on chromosome imbalances, a finding that may shed light on how the addition or deletion of genes and the organization of the genome affects organisms, according ...

Double identities lie behind chromosome disorders

Jul 08, 2007

Chromosome disorders in sex cells cause infertility, miscarriage and irregular numbers of chromosomes (aneuploidy) in neonates. A new study from Karolinska Institutet published in the scientific journal Nature Genetics shows ...

Recommended for you

The origin of the language of life

Dec 19, 2014

The genetic code is the universal language of life. It describes how information is encoded in the genetic material and is the same for all organisms from simple bacteria to animals to humans. However, the ...

Quest to unravel mysteries of our gene network

Dec 18, 2014

There are roughly 27,000 genes in the human body, all but a relative few of them connected through an intricate and complex network that plays a dominant role in shaping our physiological structure and functions.

EU court clears stem cell patenting

Dec 18, 2014

A human egg used to produce stem cells but unable to develop into a viable embryo can be patented, the European Court of Justice ruled on Thursday.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.