Mutation is the source of ALL variation in color, so what I am going to try to do is correct/clarify the misinformation that has been posted here about how inheritance/mutation in genes works.

I see a lot of confusion here due to the way certain words are used in common language and the way they're used in science.

EX: "mutation". Mutation is used as both a verb and noun in biology. A mutation in biology (as stated in the first line of the first post) is just a CHANGE in a genetic locus. So it's used as a verb when describing the fact that there has been a change in the DNA sequence, "There was a mutation in gene {G1}, substituting one nucleotide for another to form gene {G2}" and as a noun to describe the result "The {a} allele is a mutation of the {A} allele of the gene for pigment". That's all.

There is no additional requirement/understanding that once it is passed on to offspring it is no longer considered to be a mutation. IT IS STILL A MUTATION, only then it is an inherited one. A difference between what the DNA sequence was, and what it is now. Whether a mutation is heritable and passed on to offspring is a separate consideration, it does not change it from being a mutation in the first place.

The word mutation is used in common conversation to refer to a BAD physical change that occurs during the post-birth lifetime of an organism, that then affects the physical condition of that organism itself. True mutations more often affect offspring, because they happen in germ cells or during development. Like the "limb in the middle of your forehead" comment from the first post (more accurately, something like this is called a developmental defect), & like many popular culture icons (Killer Tomatoes, Swamp Thing, Teenage Mutant Ninja Turtles ), which were "mutated" from "normal" things into "mutants" by radiation or toxic chemical waste.

THERE IS NO SUCH NEGATIVE CONNOTATION TO THE TERM MUTATION IN GENETICS. It is neither a "good" or a "bad" thing, it's JUST A CHANGE.

There are also major differences in scale that are being obscured in this thread. Change/mutation can be at the level of the chromosome (which in genetic terms is huge and contains 10000's of genes), or just a single base-pair substitution/insertion/deletion of the DNA (2 molecules, 1/1000 of an average single gene), this small-scale mutation happens all the time, it's happening in your body right now! Sometimes they're good, sometimes they're bad (cancer) and sometimes they have no effect at all. Large-scale/chromosomal mutations are more rare, b/c they affect whole suites of genes and are much more likely to have negative effects, but they do happen.

ALL ORGANISMS HAVE MUTATIONS, by definition, we're all "mutants", b/c through evolution of the genetic code since the beginning of life, we all have many "changes" that have been made to our DNA. I am a pigment mutant! I have blonde hair, which is a homozygous recessive genetic trait, and a MUTATION, b/c my Homo sapiens ancestors (and yours) long ago all had dark hair, and somewhere along my lineage there was a mutation (which has occurred and re-occurs throughout human history in different populations) that led to light yellow hair. My husband loves my mutation! And I his mutant blue eyes, which are a homozygous recessive genetic trait that is a mutation! There's nothing judgmental about the correct, biological use of the word.

There is no reason to be defensive about whether the beautiful cream-fur/burgundy-eye gliders, or any specially-colored gliders are the result of a "mutation" or not. They are, whether it was long ago in the ancestors of their parents, or during fertilization/gestation of this pregnancy (which is possible, I'll explain below) makes no difference. It is still a mutation, neither a good or bad thing, just a change from an original genetic state. You can distinguish whether it's a NEW mutation (happened in this organism) or an OLD mutation (happened in a previous generation), but they're all mutations.

2.Why "albinism is not a mutation because it exists/has existed in all animals & is a heritable recessive genetic trait" statements are incorrect:

1st.The opposite of "mutation" is not "normal". There really is no opposite, only "ancestral and derived", i.e. you're not the opposite of your parents/ancestors, you're the descendant/derived of them.

2nd. Albinism does exist in all animals, but that is NOT because the "mutation happened a long time ago and has now evolved to be "normal". There are many different causes (genotypes) and forms (phenotypes) of albinism, they are not all 1 thing. Some of the genes responsible for some kinds of albinism arose via mutation long ago and have been passed on, but some happen and are happening RIGHT NOW!

Albinism is common because the underlying basis of coloration (i.e. pigmentation) is shared by all animals, and these mechanisms are even more similar among mammals b/c we're very closely related to each other, and changes (mutations) in the genes for pigmentation are common (b/c not fatal to the embryo) and so arise OVER AND OVER AGAIN, spontaneously, especially in captive-bred organisms, where breeding is much more frequent & survival isn't dependant on camouflage.

Thus, the mutation could be inherited, but could also have occurred this year! It could've been a mutation in the DNA of a parent's germ (sperm/egg) cells, that then went on to make a baby, or even during development of the babies in question, through a mutation (just a change!) in the DNA sequence during development that leads to lack of pigment and/or pigment deposition. In both of these scenarios, these parents are unlikely to ever have albino offspring again.

For an albino's offspring, this change may or may not be heritable, it depends on whether it was a mutation in the "germ" (reproductive) cells' DNA or "somatic" (non-reproductive) cells' DNA.

If it is a somatic cell mutation, IT IS NOT HERITABLE, it just means a change in the genes of skin cells results in lack of pigment, but that albino will have offspring the color of a combo of its parents because it cannot pass on the mutation, as its germ cells do not have the mutation.

If instead it is a mutation in the germ cells, then the trait will be passed on to the albino's offspring, but will only be expressed (i.e. show up in the "phenotype", the outward appearance of the organism) if the offspring are "homozygous recessive" for the trait. This concept seems to be confusing as well, so let's explore it:

Genes are the instructions for how to build proteins. Recessive means that the gene does not make a protein, or it makes a non-functional version of the protein. A dominant gene makes a functional protein. You only need one FUNCTIONAL (dominant) gene to make enough of most needed proteins, so to express the recessive phenotype, an organism has to have only the recessive {a} gene, not the dominant {A} in order that no protein is made. How does this work? See below:

A "gene" is named for the trait it gives instructions for (like the gene(s) for pigmentation) and an "allele" is one of the different version/forms of that gene. Ex: I'm using{A}and {a} as alleles of the gene for pigmentation. Why?->

Diploid" means we have 2 sets of genes (1 from each parent). If we designate the gene for pigment as {A}, then the recessive form (which does not make the pigment, due to mutation(s) that occurred recently OR in the distant past) is {a}. This is because genes are assigned names based on the expression of the non-functional (also called the "knock-out") version, in this case "albinism".

Having 2 of the same version (allele) of a gene is being "homozygous", having different versions is "heterozygous". So the "genotype" (what genes you have, as opposed to "phenotype", what genes you show) {AA} is homozygous, as is {aa}. {Aa} is heterozygous.

"Homozygous recessive", therefore, means you're genotype {aa}, which has a phenotype of albino. Homozygous dominant means you're genotype {AA},and your phenotype is pigmented. Heterozygous means you have a genotype of {Aa}, and a phenotype of pigmented, because 1 copy/version/allele of the gene is enough to make the protein to give you color. Being {aa} for a gene does NOT mean that gene isn't the result of a mutation, it means you have 2 copies of a version of a gene that doesn't make a protein that the functional/dominant {A} version makes, THAT'S ALL.

As far as offspring, during the formation of "gametes" sex/germ cells like sperm & eggs, the "diploid" genotype is divided, so in 4 eggs or sperm from an {Aa} parent, 2 will be {A} and 2 will be {a}. This means that through INHERITANCE [see above for how parents can make different offspring NOT through inheritance]{AA} parents can only make {A} gametes, {aa} parents can only make {a} gametes, but {Aa} parents can make EITHER {A} or {a} gametes.

Gametes are then combined through fertilization to make a new diploid baby, which (barring a NEW mutation) will follow the same rules, previously outlined, of genotype/phenotype.

Punnett Squares allow you to attempt to predict the likelihood of offspring genotype & phenotype, knowing the above ratios. But it is not a guarantee, it's a probability, like when you say you have a 50:50 chance of flipping a coin and getting heads vs. tails. This is true, and with many repeat tosses of the coin it will work out, but if we only toss it twice? Birth sex ratio likelihood in humans are 50:50, but how many people do you know that have 2 sons or 2 daughters instead of the "likely" one of each?

Especially if the genetic basis for the trait is not truly known, Punnett squares may not tell you much, i.e. we may assume that an albino is {aa} due to inheritance, but they may in fact be {AA},and have a somatic mutation that makes them albino, but is not passed on. This doesn't mean genetic principles are wrong, but rather that more study is needed to determine the specific genetics of the situation.

Now that we're clear, those adorable little gliders could come from genotypically {AA} parents, and have a NEW mutation in BOTH the genes for deposition of pigment in the eyes and the skin/fur. Thus, they could be "albino-burgundy" in their eyes, and have a related, NEW mutation/change/reason for being creamy with a taupe stripe (not-albino), which is not due to their parents genotypes. In this scenario, the NEW mutation may or may not be heritable, as I said before it depends on whether the babies have this mutation in their germ cells or their somatic cells.

OR, it could be heritable, because of some recessive (non-functional) OLD mutation/version of the pigment gene that the parents happen to both carry {Aa} and passed onto the twins, such that each twin is {aa}.

And this brings me to my last point. I have a PhD in biology, I am a molecular biologist by training, I work on the genetics of marine animals for my research, and I am a biology instructor at a university...but I would never attempt to obscure/hide the data about genetics/biology from people based on the consideration that the truth is "too hard for laymen to understand/accept". This is insulting to them and our field, a good scientist/teacher can convey information to everyone, that's our job. Here's an M.SC. in genetics making statements that are obfuscating, untrue misconceptions about genetics, even sort of slandering one's own field by saying the "science" of genetics in quotes.

The fact that we can't yet know exactly what's up with these babies doesn't mean genetics are somehow foggy, but that the practical determinations are made with time and breeding crosses. A geneticist would know that. We do everyone a disservice when we give them bad data...