hey, we had a thread getting off topic and I was too interested in both discussions to let either die, so I was hoping we could move the x-linked discussion here. Here is the topic that brought it up, in case you wanted to see:

http://www.glidercentral.net/ubbthreads/ubbthreads.php/topics/980582/Since_it_came_up_leu_to_leu_br

The basic question is: can a producing male from a sterile mosaic line pass on sterility or does the fact that he is producing mean it cannot be passed through him?

Great topic I myself have been wondering that and have heard many different things so it would be nice to finally know the correct answer!

LOL... hopefully Adri will have time to elaborate on this soon. But in the meantime, i thought this thread is so important so that we can all understand more about the genetics and what we are dealing with.

Adri and I did talk about Preston's sterile background, and that he should not be bred to leus. I respect that and I will follow it. However, I believe that I and everyone else should have a better and deeper understanding of the reasonings behind these types of decisions so that we know WHY we don't breed sterile lines to leus, and WHY it is so important. I could have just called Adri and asked for her explanation, but I thought the whole community could get better educated by this discussion.



So... here we go!

Please do I would like to know more.

First off... it is not the male that carries the sex linked trait for sterility. It is the female who is the carrier and she passes the sex linked sterility gene to her daughters.

I know you guys have been waiting on me and really though I have a passion for genetics I am by NO means a geneticist! I have been trying to put it all in to words that everyone can understand without having to pull up a reference manual with no luck....So I found a pretty good site that explains it in laymens terms. It is a pretty good read I hope you guys enjoy it! http://www.answers.com/topic/xy-sex-determination-system

That was my original question/concern. If sterility is x-linked, and there are males in the lineage between your glider and the sterility... why does it still matter?

Sorry for putting you on the spot, Adri. And thank you for the link!

Here is another I have been looking at: http://en.wikipedia.org/wiki/Sex_linkage

Nadine and Judie, you are both making sense to me:

If you read the link I posted it explains that a male gets just one copy of a recessive mutation on their x chromosome but their bodies will treat it as if they have 2 copies - so dominant or recessive makes no difference to them, it is expressed like a dominant gene in them either way - so if you do not see the problem in him, he does not have it, HE CANNOT BE A HET FOR THE PROBLEM.

He cannot pass it on to his sons because an x-linked mutation, by definition, will only be on an x chromosome and sons only get an x chromosone from their mother. They get a y from the father, that is what makes them a male.

The benefit of having the mutation be sterility is that it is self limiting. If he HAS the defect, he will not produce offspring, so he cannot pass it on to his daughters. So they, too, are clean.

But there is a hitch. What if the sterility is not from one gene but several genes? What if he was bred out enough to fix one or some of the genes enough that he could still produce, just not at full capacity? That infertility could still be passed on (not the complete sterility, once a gene is out of him, it is out and remember he already got some of the bad genes out of him so he can no longer pass on sterility, just the infertility he now has).

Remember that he gives an x to his baby girls and a y to his baby boys. So his girls, getting his x, will still be carriers of the infertility we saw in him. His boys, however, get no x from him. Since the disorder is only passed through the x his male offspring would be completely free of the defects and, of coarse, unable to pass it to any offspring.

Please ask for clarity or correct me if there is a hole in my logic. But I see no reason why we cannot consider all males who are from sterile lines, but the "sterile line" is only on their father's side, to be completely clean mosaics with zero chance of sterility in the line after them.


I feel I should add a disclaimer that I own no mosaics nor any animals that have any sterility anywhere in their line, so I have no vested interest other than liking to get to the bottom of things

WOW... great explanation. IF that were to be true, than any joeys from Preston would NOT be at risk for the x-linked sterility...

BUT Adri explained it in a way that it seemed that there was still always a risk.

That is why I was curious as to why it is still treated as a defective lineage even if any x-linked genes did not continue on in the line.

And yes, I do have a vested interest... but more than that I have an unsatiable curiosity about the genetics.

There is also the possibility that the sterility, although known to be x linked, is also the process of a combined effect from other genes, on other chromosomes. The mosaic population is still relatively small so even though a male glider might not have the x chromosome that causes full sterility, he may have, and be able to pass on, other genes to his offspring that contribute to the problem - this would be the potential infertility just mentioned.

In a small population such as the sub-population of mosaics "from sterile lines," the risks of a glider getting two copies of any genes not on the x chromosome, but contributing to the sterility, would be greater than in a population that has no history of sterile lines.

Genetics are complicated and it is rare that only ONE gene is responsible for a 'syndrome'. Usually multiple genes located together on a chromosome are involved. Chromosomes are also not entirely static. In the process of duplicating themselves entire sections or ends can be exchanged in the process. Again, in a small population there are limited variations in the group's common genetics and more chance for an individual to receive two copies of recessive genes that are expressed in either positive or negative traits.

We are uncertain if this is x-linked??? I had always assumed that was a conclusive fact based on how matter of factly it was always stated to me. I should have wondered how someone could conclusively know that.

Ok, then, I have heard that SOME producing males from this line (the sterile line) exhibit some level of infertility. Is this true? And, especially, is it true early on after sterility is bred out? Does it seem to be running in families (like a producing male AND his son had it)? No names needed!!! Just is it true or not and what observations have been made about it?

It is presummed to be x-linked because we see the sterility in the males but not the females. But no dna testing has been done.

ok, well if that is why then I believe it COULD be anywhere except on the y chromosome. Its good to rule one out, at least

Have there been any abnormalities in the females that produce sterile males? Do they seem to have any decreased fertility or pull joeys more often or produce mutated joeys more often than is average? Some genes that cause infertility in males also cause slight problems in female fertility and/or cause increased genetic mutations in the offspring. Knowing about this will likely not help tell us where the gene(s) are, but it helps to have all of the pieces of evidence that are out there just in case.

On the decreased fertility- the sterile line one of my mosaics is from- his mother tends to only have 1 or 2 sets of joeys a year. Is that because she's from sterile lines or does she just prefer to not have joeys too often? It's hard to say.

My boy from this line proved out- he didn't produce as young as some males do, he was well over a year old. So he could be slow on the fertility side and be like his mother & only have 1-2 joeys a year. I neutered him when his daughter was 4ms oop, they didn't have any others during that 4 months. So who knows

Its so hard to speculate. I assumed that sterility is x-linked because isn't it in other animals?

And if there is lingering infertility, when do we call it infertility or the end of it... in my example, Preston got both girls pregnant when he was 6 months old... and when they pulled, they had joeys IP again within a month. So... there is obviously NO issues with him being slow on the producing end.

I wish it wasn't so expensive to do genetic testing! It would be so interesting to see what the genes are for these things.

The problem with doing genetic testing is not only the expense but the HUGE undertaking of having the testing done on thousands of gliders with lineage and health histories so the data could be compared and further studied.

Without the lineage for each glider studied, and having multiple generations of related gliders studied, there would be no standard to compare an individual glider's DNA to.

So true, Candy.

Yeah, it would have been fun to get to the bottom of this. We can make educated guesses if lots of people contribute their experiences with gliders from this lineage; but as far as I know, even with their accounts there will be no way to know with certainty if it is x-linked partially, completely, or not at all.

IF we knew for certain that it bred out completely every time after one producing male and his son, then we could conclude it was x-linked. If any infertility lingers at all after a producing male and his son, then it is either partially x-linked or not x-linked at all.

The most important question is: is there any non x-linked portion of it that is dominant? If it lingers after a producing father and his son, and especially if it tends to run in families despite being very bred out (low coi and breeding to lines without sterile mosaics in it), then it most likely is dominant.

If it was dominant about half of the joeys would have the lessened fertility and pass it on. You would be able to see it, but not without breeding the animal, and even then it may not be obvious, especially in females. By the time you figure it out they may already have grandchildren about half to a quarter of which would also have the defect and you would not know which ones until you bred them (and some may slip through the cracks even then).

It would theoretically eventually become less and less % of the population every generation but would never completely breed out of the population like a recessive gene unless we started selecting it out like nature does (by not breeding effected individuals or their offspring). It would be VERY difficult to breed out of a recessive color population, if it somehow got in. I'm not pretending to know if this is happening. I have no idea. I hope not. And this is not a special scenario for this gene, this would be the case for any dominant gene that remains hidden until after the animal has had offspring. Again, I'm NOT saying this is happening, I mentioned the signs above that would suggest it is happening, I'm just explaining what would be the prognosis if we did find out this includes a dominant gene.

And Nancy, with your mosaic family, yes, this COULD be because your animals are from sterile lines and it has not been completely bred out; it would be the most likely scenario; especially since this male is first generation from sterility (it would be interesting to know how his sons would produce) But with a sample size of 2, the standard deviation will be very close to 2. Simply meaning that we cannot draw conclusions for the whole population based on 2 animals. Like I said, if we were seeing trends like this, it would become very suspicious. But with just 2 animals, although it is likely, it COULD also be anything: maybe they have another mutation and are pulling joeys because of it, maybe they aren't eating all their food and their nutritional balance is not ideal for breeding, maybe they have a completely different mutation for fertility issues ... The list is endless.

Thank you for being willing to say so and help with the greater good of the gliders in this line! And I want to make sure I say that I am in no way implying that your animals have bad genetics or are not healthy, I'm just saying there are endless reasons this could be happening to anyone's animals; the sterility in the line makes it suspicious, but that is all, no conclusions can be drawn.

And I want to make sure not to be confusing, I am NOT saying your animals are showing evidence of the dominant gene I spoke of above. You would have to breed a son of your male to contribute to any evidence for or against that.

If the community wanted to get an educated guess about what is going on, they would need lots of breeding accounts from this line; both the females and producing males; whether mosaic or not; but with sterile line mosaics in their ancestry. How far are they from the sterility and how do they produce (some of the females may still be producing sterile; do they show any other symptoms?)? and if you got really ambitious, even map out which family lines seem to have this lingering problem (if there is any lingering problem). This is up to people who know mosaics and have a vested interest in their line; if they decide it is important to them to know. I do not know mosaics; but think they are beautiful animals and wish them and their pet people long, healthy, fruitful lives