changing number of chromosomes?

[Eddi]

This has come up on some other threads....

How can the number of chromosomes a species has change as the species evolves?

For instance how can two species that share a common ancestor each have different numbers of chromosomes?

How does this work????

What happens????

 

[sun rise]

From Google bard - Prompt What research has there been on changes in number of chromosomes as part of evolution? Provide references

Here are some references to research articles on changes in chromosome number as part of evolution

• Evolution of Chromosome Numbers: Mechanistic Models and Experimental Approaches: Estimating chromosome sizes from karyotype images enables validation of de novo genome assemblies
• Chromosome Evolution in Connection with Repetitive Sequences and Epigenetics in Plants: Chromosome Evolution in Connection with Repetitive Sequences and Epigenetics in Plants
• Evolutionary Mechanisms of Varying Chromosome Numbers in the Radiation of Erebia Butterflies: https://royalsocietypublishing.org/doi/10.1098/rstb.2019.0539
• Can changes in the number of chromosomes affect health and development?: MedlinePlus: Chromosomes & mtDNA

From the same question:
Whole Genome Duplication (WGD)

• WGD is considered a major driver of evolution, leading to rapid diversification and the emergence of new species.
• Research on WGD has been conducted across various organisms, including plants, animals, and fungi.
• Studies suggest that WGD can provide raw genetic material for evolutionary innovation, allowing for the emergence of new genes, regulatory networks, and phenotypes.

Polyploidy:

• Polyploidy refers to the condition where an organism has more than two sets of chromosomes.
• Research on polyploidy has shown that it can lead to increased genetic diversity, improved stress tolerance, and faster adaptation to new environments.
• Polyploidy is particularly common in plants, where it has played a major role in the evolution of many agricultural crops.

Chromosome Fusion and Fission:

• Chromosome fusion and fission can alter the number of chromosomes by merging or breaking them apart.
• Research on these processes has shown that they can contribute to reproductive isolation and speciation by preventing successful chromosome pairing during meiosis.
• Studies have also shown that chromosome fusion and fission can lead to changes in gene expression and regulation, with potential impacts on organismal development and morphology.

Aneuploidy:

• Aneuploidy refers to the presence of an abnormal number of chromosomes in an organism.
• While often detrimental, research on aneuploidy has shown that it can play a role in evolution by driving rapid phenotypic changes and promoting the evolution of novel traits.
• Studies have also shown that aneuploidy can be associated with certain human diseases, such as Down syndrome and Turner syndrome.

 

[libre]

How can the number of chromosomes a species has change as the species evolves?

I'm not familiar with studies on chromosomal quantity and evolution, gave it a google but it's too complicated for me.

However I do know that we have many good examples of chromosome mutation within our species.

For instance:
Turner syndrome where human beings are born with only one chromosome.
and
Down syndrome where humans are born with an extra.

 

[Quintessence]

Yes. Happens all the time in plants. Less routine in animals, because animals are boring like that.

 

[Heyo]

Possibly the most popular fusion of chromosomes:

"Human chromosome 2 is a result of an end-to-end fusion of two ancestral chromosomes.[7][8][9] The evidence for this includes:

• The correspondence of chromosome 2 to two ape chromosomes. The closest human relative, the chimpanzee, has nearly identical DNA sequences to human chromosome 2, but they are found in two separate chromosomes. The same is true of the more distant gorilla and orangutan.[10][11]
• The presence of a vestigial centromere. Normally a chromosome has just one centromere, but in chromosome 2 there are remnants of a second centromere in the q21.3–q22.1 region.[12]
• The presence of vestigial telomeres. These are normally found only at the ends of a chromosome, but in chromosome 2 there are additional telomere sequences in the q13 band, far from either end of the chromosome.[13]

We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2. — Jacob W. Ijdo[13]" from Chromosome 2 - Wikipedia