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Salvistar those would be considered Chimeric and or Somatic Mutation.

Somatic Mutation: A Somatic Mutation is an effect that happens in the womb switching off the expression of a gene in an area on a horse. Somatic Mutations are very rare, however, thanks to the internet and the interest in seeing rare and unique horses it is getting easier and easier to find examples of rare coloured horses.


Mosaic Chimera Versus Somatic Mutations:

The most difficult part with coming across a unique horse is knowing if it is indeed a Somatic Mutation or if it is Chimera. Mosaic Chimera and Somatic Mutations can have very a similar phenotype. Therefore it can be impossible to tell if a horse is Mosaic Chimera or has Somatic Mutation without DNA testing for multiple sets of DNA.

am i right Ammit? about the Chimera and Somatic mutation?

Not exactly Baya. Somatic mutations are rather common we just don't see them that often. And be sure to quote if you take other people's words ;)

Somatic mutations are a type of mosaicism so is not wrong to call this horse mosaic. His specific type of mosaic is most likley somatic. The mutation does not go back to his genital area so it is very unlikely he can pass it on to offspring. Somatic means in the body cells only.

If a horse has a white area of odd color it is more likley this horse is a somatic mutation. Darker areas are more likley to be chimeric then white though they are often still somatic. (FRS Reckless Dan is a white stripe brindle confirmed chimeric but he is half gray horse half not) That is because just about any mutation can turn off pigment production and break something (all white markings are broken pigment) but there are very few situations that will result in more pigment being made. It also is astronomically unlikely for the same mutation to happen twice. So if a horse has a white area it is not gray or roan or any other gene you already know. It might be roaned looking it might even be on Kit but it is not the roan gene.

This is an ongoing discussion I thought you might like to see. I will start where I drop into the convo.


Huntandjump Horsegame Somatic is just a type of mosaic.

NL ^^^You mean Mosaic is a type of somatic mutation.

CNS So does that mean that you could use mosaic and somatic interchangeably? Possibly?

Huntandjump Horsegame No I do not. All somatic mutations are mosaic, not all mosaics are somatic mutations. A mosaic is when one individuals has more then one variation in its DNA caused by an error/mutation. A somatic mutation is a mosaic animal where the mutation has only effected the somatic (non sex cells) of the individual.

So CatchABird and Lorando B are both mosaic horses. They both have two different variations of DNA in them but Lorando B is a somatic mutation, he can not pass on his mutation to his foals. His sperm does not have the mutation. However CatchABird was NOT a somatic mutation he was a de novo mutation. Because his mutation was passed to his foals it is completely incorrect to call him a somatic mutation. Somatic always means non inheritable/ not in the sperm eggs.

Mosaic and somatic mutation do not mean exactly the same thing but it is not wrong to use the two terms pretty interchangeably. Mosaic is just a more broad term. The term somatic mutation gets a bit abused.

Huntandjump Horsegame If whatever mutation Stetson Blue has, is in his sperm then it is incorrect to call him a somatic mutation and he should be called a mosaic. If it is a stable and inheritable new allele then it can be called a de novo mutation but it may be impossible to ever prove that as new gene founders often don't express their gene in the same way their offspring do. (Because the founder is a mosaic and the foals are not) That is why often the term mosaic is used because it can sometimes be impossible to tell of the ovaries/testes are involved.

Here is a good run down of mosaic versus chimeric from Colorado State.
http://www.vivo.colostate.edu/.../medgen/chromo/mosaics.html

AH Very interesting!

NL I don't agree that ALL somatic mutations are Mosaicism. Mosaicism is caused by two genotypes in a single zygote. That does not explain somatic mutations involving cell migration during fetal development. For example horses like DA Remote Control who have the swirly white patterns scattered across the body. These are theorized to be white patterns that didn't make it to their destination. Likely meant to be leg white. Or the somatic mutations where certain modifier genes are "switched off". The calico tobiano's where it is theorized that the tobiano white pattern interfering with the cream gene causing the cream gene to be "switched off" in spots. I also don't believe all of the "bloody" markings on grays are the result of two genotypes but again mutation occurring during fetal development causing the gray gene to be "switched off" in areas on the body. These types of things fall under the definition of somatic mutation which is alternation to the DNA AFTER conception. They also don't affect germ cells which is why these are not heritable. Mosaicism does affect germ cells which is why it can affect offspring and make some animals sterile. Saying all somatic mutations are mosaic when not all somatic animals have two genotypes does not make sense.

NL I will say I was wrong in saying mosaic is somatic I was thinking of that incorrectly.

Huntandjump Horsegame If you read the link I posted you can see that even animals that have identical DNA strands but different genes being expressed or silenced are mosaics. Tortiseshell cats ARE mosaics even though they do not have a mutation. They have two different types of cell lines. The have orange producing cell lines and they have black producing cell lines. Even though those lines are identical in a DNA sequence they are still behaving differently so that animal is a mosaic.

You are saying these things are not genetic mutations. I agree with you that some of them likley are not. They are gene silencing. But the word mutation is literately in the term somatic mutation. If no mutation occurred then the animal can not in way be a somatic mutation. The mutation part is the key. These animals are mosaics. If you are getting two types of cell expression but there was no mutation then it can not be a somatic mutation it can only be a mosaic.

You are also not using the term somatic correctly. Somatic does not mean alteration after conception at all. Somatic means an alteration of somatic cells. The definition is not in any way concerned for when the mutation occurred. Many cancers are somatic mutations. In biology we have two major classes of cells, somatic cells (anything that can't make sperm or eggs) and gametes (anything that can make sperm or egg). Somatic mutation is a mutation in a somatic cell. If it is not a mutation or if it is not only in body cells then using the term somatic mutation is incorrect.

"Mosaicism does affect germ cells which is why it can affect offspring and make some animals sterile." This is not what mosaic means at all. You are describing a gamete mutation. Any mutation that effects the gametes is a gamete mutation. Mosaic means more then one type of DNA expression. It does not mean it effects only body or only sex cells, or has to have mutations or anything else.

Mosaic, gamete, somatic, and mutation are bio 101 terms. They have set defined means that are easy to look up online. I don't want to be mean but I am kind of shocked that not one but two group admins don't know the definition of these terms or bothered to look them up. These are not points of debate, you can pop open just about any bio textbook and get the definition. Again I am not trying to be harsh here but I really am floored.

As an aside. I do not agree with your "meant" to be leg white theory as that does not make any sense when you know embryology and how white markings form (white leg markings are a side effect of halted pigment production NOT an intended marking to be made. White is a lack if pigment not an added on marking) . Leg markings do not migrate across a horse's body. Only pigment migrates from the spine down like that.

The first horse is actually a somatic mutation, as neither of his parents are grey. :D Which is what makes him odd lol