Question

Horses have 64 chromosomes and donkeys 62. The sterile hybrid between a horse and donkey is called a mule. In 1985 a mule named Krauss gave birth to foal named Blue Moon who was also a mule, and then in 1987 to another mule foal named White Lightning. Krauss was routinely pastured with other mules and horses but not donkeys. Explain this unusual occurrence.

Answer 1

A mule gets thirty two horse chromosomes from mother as well as thirty one donkey chromosomes from dad for a total of sixty three chromosomes. (A horse has sixty four chromosomes along with a donkey has sixty two).To know why this's an issue, we have to know how sperm & eggs are made. Also to know that, we have to get into alittle more information about chromosomes.Remember, we've 2 copies of each of the chromosomes of ours -- one of mom and one of dad. What this means is we've 2 copies of chromosome one, 2 copies of chromosome two, etc. Nevertheless, this is not completely accurate for the mules.The mule has a pair of horse chromosomes from the mother of its. Along with a set of donkey blades from the dad of its.These chromosomes are not truly coordinated sets like in a horse, a donkey, or maybe an individual. In these instances, a chromosome one is much like another chromosome one. It seems essentially similar and also has almost the identical range of A's, G's, T's and C's. For instance, 2 human chromosome 1's differ just every thousand letters or thereabouts.But a donkey chromosome does not always look as a horse one. And also the very poor mule even comes with an unmatched horse chromosome merely sitting there. In order to make an egg or a sperm, cells need to take a step called meiosis. The concept behind meiosis is usually to obtain- Positive Many Meanings - a single copy of each chromosome into the sperm and egg.For instance, let's concentrate on chromosome one. Like I said, we've one of mom and one of dad. At the conclusion of meiosis, the sperm or maybe egg has both mom's or maybe dad's chromosome one. Not each.This process calls for 2 things. For starters, the chromosomes need to look rather similar, which means they're about similar size and also have exactly the same info. This can need to do with how healthy they match up throughout meiosis.And next, at a later crucial stage, there must be 4 of each type of chromosome. Neither of these may happen entirely with a mule.Let us take a better look at meiosis to determine the reason why this's. The initial step of meiosis is the fact that many of the chromosomes make duplicates of themselves. No issue here...a mule cell is able to pull this off fine.Now we've a cell with sixty three doubled chromosomes. It's the following step that triggers the actual issue. In the following step, all of the same chromosomes have to match up in an extremely specific way. Thus, the 4 chromosome 1's all should line up together. But this cannot take place in a mule perfectly.Like I said, a donkey along with a horse chromosome are not always comparable adequate to match up. Contribute to this the unequaled chromosome and you've a serious issue. The chromosomes cannot discover the associates of theirs and this also causes the sperm as well as eggs to not get made.And so this's a huge reason behind a mule becoming sterile. But how's the silly thing living at all.Well, you will find a couple of factors. For starters, creating an unusual number of chromosomes does not matter for daily life. A mule's cells are able to divide as well as make new cells just great. That is crucial thinking about a mule went from one cellular to trillions of them.Chromosomes sort differently in standard cells than they actually do in eggs and sperm. Traditional cells (known as somatic cells) make use of a procedure called mitosis.Mitosis is just like the initial step of meiosis. The chromosomes each make duplicates of themselves. But rather than matching up, they simply sort into 2 new cells. And so for the mule, each cellular ends up with sixty three chromosomes. No matching has to occur. And the lone horse chromosome of ours is okay.The other reason a mule is in existence is the fact that nothing on additional or even lacking chromosome causes it any damage. This seems obvious in the beginning except that generally having more DNA causes severe issues. In people, additional chromosomes generally lead to miscarriages. Occasionally though, a kid can survive with an additional chromosome.For instance, people with an additional chromosome twenty one have Down syndrome. Having all of the additional genes on that additional copy of chromosome twenty one cause the symptoms related to Down syndrome.So having extra chromosomes oftentimes leads to problems that are real. However the mule is by and large OK..The additional genes mustn't be that big a deal for the mule. Put simply, additional genetics on the horse chromosome don't trigger trouble for the every single day life of a mule.Indeed mules are sterile since horse as well as donkey chromosomes are simply too different. Though they're alive because horse as well as donkey chromosomes are similar adequate to mate.