A new technique using stem cells and gene editing is now considered in the scientific world a major accomplishment and one that the team is hoping will uncover more about the manner rearrangement of chromosomes can affect the way animals are evolving over time.
A ScienceAlert report said that changing the number of chromosomes an animal has can takemillions of generations to occur in nature through the course of evolution, and currently, scientists have been able to make such changes in lab mice in a "relatively blink of an eye."
In chromosomes, those protein strings and DNA inside cells, genes could be found, inherited from parents, and blended together to make an individual who he is.
For mammals such as mice and even humans, chromosomes usually occur paired. However, there are exceptions like the ones in the so-called "sex cells."
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A laboratory technician holds a lab mouse before operating on it as part of a stem cell research program at the National Institute of Biological Sciences in Zhongguancun Science Park in Beijing.
Imprinting Process
Unfertilized embryonic stem cells are typically the best starting place for tinkering with DNA. Without that additional set of chromosomes provided by a sperm cell, nonetheless, deprives the cells of an essential step in terms of negotiating which genes in which chromosomes will be marked active to do the job of constructing a body.
Called "imprinting," this process was a stumbling block for engineers who are keen to reconstruct large chunks of the genome.
According to Li-Bin Wang from the Chinese Academy of Sciences, genomic imprinting is often lost, and which genes that need to be active vanishes in haloid embryonic stem cells, restricting "their pluripotency and genetic engineering."
Wang also said they recently found that by deleting three imprinted regions, a stable sperm-like pattern could be in the cells.
Chromosomes Fused
With those three naturally imprinted regions lacking, lasting chromosome fusion was plausible. In their study published in the Science journal, the researchers fused two medium-sized chromosomes and the two largest chromosomes in two different orientations resulting in three different arrangements.
The fusion of the medium-sized chromosomes was found to be the most successful when it comes to the genetic code being passed on to the mice offspring, though breeding was slower compared to normal.
One of the 1 and 2 fusions didn't produce mice offspring, while the other produced mile offspring that were larger, slower, and more anxious compared to those from the fusion of chromosomes 4 and 5.
The study investigators reported that drops in fertility are down to the manner the chromosomes are separating following alignment, which does not happen in an ordinary way.
Karyotype Changes
As indicated in a similar Collective Spark report, it reveals that critical to reproductive isolation, a key part of species being able to evolve and remain separate.
Zhi-Kun Li, a biologist, also from the Chinese Academy of Sciences said, the lab house mouse has kept a standard 40-chromosome karyotype, or the whole picture of chromosomes of an organism, after over a century of artificial reading.
Over longer periods though, karyotype changes caused by chromosome rearrangements are typical. Mice have 3.2 to 3.5 rearrangements per million years, while primates have 1.6.
To put this into context, unusual leaps in chromosomal rearrangement have helped in the direction of evolutionary paths of our own ancestors.
Related information about chromosome engineering is shown on Kurzgesagt's YouTube video below:
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