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CoastalPizza t1_j9fvswx wrote

A mule has 32 horse chromosomes and 31 donkey chromosomes. A total of 63 chromosomes. Normally, an organism would have two copies of one chromosome, one from the mother and the other from the father. However, for mules, they will get two different sets of chromosomes since the mother is a horse, and the father is a donkey. These genes will not exactly be matched sets, but they are still relatively similar (enough to produce the mule offspring in the first place). To reproduce, a process called meiosis will happen, in order to get one copy of each chromosome into the sperm or egg. During this process, the chromosomes will need to “match up” to another. Unfortunately, the donkey and horse chromosome are not similar enough to pair. Additionally, the mule will also have an extra unmatched horse chromosome, so sperm or eggs are unable to be made.

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Unicorn_Colombo t1_j9htljs wrote

It should be noted that there are organisms where populations differ in their karyotype while still being compatible. This is quite common among rodents, where population of the same species can be easily identified with their karyotype, but still produce viable and fertile offspring.

So I don't know enough about this particular case to say where exactly is the problem, but just having a different number of chromosomes isn't such a barrier as people often make. Yet, it is still likely related because chromosomes represent organisational units. During meiosis, there are multiple steps where the material is divided. An unequal distribution might possibly be the cause, but again I don't know enough about this particular case and I would have to speculate.

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Dalenonne t1_j9hk9ug wrote

Is it like male down syndrome people are sterile and females have difficulty combining with 'normals' contribution?

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BenCarburetor t1_j9jb2z4 wrote

They have different amount of chromosomes? But they seem to be such closely related animals.

Are there other closely related animals that have different number of chromosomes? Like between duck and geese or tiger and lynx, for example?

Does this thing also happened with plants and fungi?

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HannahMarieArtistry t1_j9iq206 wrote

Thank you this is fascinating! Do they still present as either male or female in some way, even though they can’t produce sperm or eggs? Or are all mules physically non-binary in some way?

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