Researchers from the Institute of Zoology of the Chinese Academy of Sciences announced the first controlled merger
For short periods of time, chromosomalthe set in one species remains stable, but on the scale of evolution it is constantly changing, the scientists explain. For example, during a million years, rodents undergo from 3.2 to 3.5 rearrangements of the chromosome set, and 1.6 in primates. This small number defines, for example, the difference between gorillas and humans.
In their work, scientists used stemcells from unfertilized mouse embryos. The complexity of genetic modification is due to the fact that some genes are activated only if they come from one of the parents (mother or father). This process is called genomic imprinting. At the same time, unfertilized embryos contain only the mother's DNA, so not all changes will be active in the modified animals.
To get around this limitation, researchersblocked three regions responsible for genomic imprinting. After that, they modified the DNA of several embryos: in the first group, two medium-sized chromosomes were combined (connecting the top of the fourth chromosome to the bottom of the fifth), in the second and third, the two largest chromosomes (first and second) in different configurations.
A genetically modified mouse with the 4th and 5th chromosomes combined. Image: WANG Qiang
The study showed that the merger of the secondchromosomes with the top first resulted in premature offspring, while the opposite pairing produced larger, more anxious, and slower individuals. However, only mice with fused chromosomes 4 and 5 could reproduce with wild rodents, but at a much slower rate than standard laboratory mice.
The authors note that the resultsstudies show how chromosome fusion limits interbreeding with other individuals, leading over time to reproductive isolation and the formation of a separate species.
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