And how can animals descended from a common ancestor have different numbers of chromosomes?
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There’s a lot to unpack here… They don’t have a single stand. A chromosome is a protein paired with a single molecule of DNA. We have a bunch of them. Animals and plants also have a bunch of them, and they do different things and have different effects if they get messed up. Chromosomal fusion over time is generally considered the answer to why there are differing numbers of chromosomes in different species.
There’s a lot to unpack here… They don’t have a single stand. A chromosome is a protein paired with a single molecule of DNA. We have a bunch of them. Animals and plants also have a bunch of them, and they do different things and have different effects if they get messed up. Chromosomal fusion over time is generally considered the answer to why there are differing numbers of chromosomes in different species.
When a cell divides, it needs to duplicate its DNA so that the new cells each have a complete copy. Part of doing this is to divide the DNA strand into chunks. These chunks are “chromosomes.” I don’t know the exact mechanism for how the DNA “decides” to divide itself up into a different number of chromosomes, but different organisms have different numbers of chromosomes because it divides its DNA up into different numbers of chunks when replicating.
During this replication process, there can be errors. Sections of DNA can be rearranged, copied, or deleted. In this manner, an organism can end up with new cells that have different number of chromosomes. If this mutation happens in the creation of gamete cells, then those mutations can be passed on to potential offspring.
When a cell divides, it needs to duplicate its DNA so that the new cells each have a complete copy. Part of doing this is to divide the DNA strand into chunks. These chunks are “chromosomes.” I don’t know the exact mechanism for how the DNA “decides” to divide itself up into a different number of chromosomes, but different organisms have different numbers of chromosomes because it divides its DNA up into different numbers of chunks when replicating.
During this replication process, there can be errors. Sections of DNA can be rearranged, copied, or deleted. In this manner, an organism can end up with new cells that have different number of chromosomes. If this mutation happens in the creation of gamete cells, then those mutations can be passed on to potential offspring.
For most animals, DNA is not a single strand: each chromosome is a separate strand.
The chromosome count can change due to copying mistakes:
* a chromosome can get a spare copy. With time that copy can diverge into a different chromosome.
* a chromosome can be lost during copying
* a chromosome can be torn apart, and become two
* two chromosomes can be joined together
For example, human chromosome #2 (numbered by size – so, second largest) corresponds to two ape chromosomes, that were joined together.
For most animals, DNA is not a single strand: each chromosome is a separate strand.
The chromosome count can change due to copying mistakes:
* a chromosome can get a spare copy. With time that copy can diverge into a different chromosome.
* a chromosome can be lost during copying
* a chromosome can be torn apart, and become two
* two chromosomes can be joined together
For example, human chromosome #2 (numbered by size – so, second largest) corresponds to two ape chromosomes, that were joined together.
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