The X Factor

[StoneCity]

I first heard about this theory when breeding horses. Since then, I try to apply it all the time. It explains how the female Chromosome X is larger and carries more genetic information than the Male Chromosome Y which is smaller and carries less genetic information. They noticed that females were responsible for transmitting certain traits or characteristics in the breed 68% of the time and males only 32%.

You can apply this theory to dogs when breeding. Now the first thing you need to know is how to read the peds using the X Factor. The second thing you need to know is the traits or characteristics expressed by each individual in that pedigree or at least the majority of them.

Let me show you how to look at a ped using the X Factor:

Let’s use an example of Mayday a male expressed as YX chromosomes

[attachment=1:dylvupqk]X Factor Male.jpg[/attachment:dylvupqk]


In order for Mayday become a Male, he received the Chromosome Y from his sire Gr. Ch. Yellow (Follow the Yellow Color Markings) and Yellow got his Y from Yellow John and Yellow John from Red Boy. Now, the question is Has Miss Jocko contributed to the genetic formation of Mayday? The X Factor theory says No. Why? Because Miss Jocko been a female as 2 X chromosomes and she gave 1 of her X chromosomes to Gr. Ch. Yellow but Yellow gave his Y chromosome to Mayday so no X chromosome information was passed on to Mayday from Miss Jocko. Mayday received his X chromosome from Dolly (follow the red marking) as she only had 2 X chromosomes to give one. Dolly receive her 2 X chromosomes one from Yazoo Cody and the other one from Lady in Red.


Now let’s do the same analysis using Dragon Lady as an example a full belly sister to Mayday. Dragon Lady is a female expressed as XX chromosomes.

[attachment=0:dylvupqk]X Factor Female.jpg[/attachment:dylvupqk]


Now Dragon Lady is a female and is made of 2 X chromosomes (XX). The X received from Dolly (Follow red color) is the only chromosome she could have received as Dolly itself is a female with only 2 X chromosomes.

Now let’s look at the top of the pedigree. Dragon Lady received the other X chromosome from her sire Gr. Ch. Yellow Male (YX). Gr. Ch. Yellow received that X from Miss Jocko. Now the question is Has Dragon Lady received any genetic information from Gr. Ch. Yellow John? According to the X Factor theory the answer is NO.

If you follow the colors you can understand how to apply the X Factor theory when you are evaluating a male and when evaluating a female. I strongly believe in applying this to all the breeding’s I do when selecting a male and a female to cross.

This approach will change the way you look at peds. It will give you a better perspective of the contributions that females brings to the breeding and will help you understand which individuals are actually contributing to the genetic characteristics of each individual.

Hope it helps more than it confuse.

[Officially Retired]

I first heard about this theory when breeding horses. Since then, I try to apply it all the time. It explains how the female Chromosome X is larger and carries more genetic information than the Male Chromosome Y which is smaller and carries less genetic information. They noticed that females were responsible for transmitting certain traits or characteristics in the breed 68% of the time and males only 32%.

First of all, thank you for the time and effort you put into this interesting theory and sharing it with us.

I have not heard of this before, but I will go through it to see if I can understand/agree with the concepts.

My opening thought is to seek clarification if it is an actual fact that the Y chromosome carries less genetic information from the sire than if he passed the X, or is this too just a theory?

You can apply this theory to dogs when breeding. Now the first thing you need to know is how to read the peds using the X Factor. The second thing you need to know is the traits or characteristics expressed by each individual in that pedigree or at least the majority of them.
Let me show you how to look at a ped using the X Factor:
Let’s use an example of Mayday a male expressed as YX chromosomes
In order for Mayday become a Male, he received the Chromosome Y from his sire Gr. Ch. Yellow (Follow the Yellow Color Markings) and Yellow got his Y from Yellow John and Yellow John from Red Boy.

Okay, I completely follow you here, as far as the sex of Mayday goes; however what I find myself doubting is the idea that all of the genetic traits are tied in to the sex chromosome (or, should I say, are lost in the absence of a Y chromosome).

Now, the question is Has Miss Jocko contributed to the genetic formation of Mayday? The X Factor theory says No. Why? Because Miss Jocko been a female as 2 X chromosomes and she gave 1 of her X chromosomes to Gr. Ch. Yellow but Yellow gave his Y chromosome to Mayday so no X chromosome information was passed on to Mayday from Miss Jocko. Mayday received his X chromosome from Dolly (follow the red marking) as she only had 2 X chromosomes to give one. Dolly receive her 2 X chromosomes one from Yazoo Cody and the other one from Lady in Red.

Okay, here is where I disagree with this theory: While Mayday is clearly a male, and while he clearly got his 'Y' chromosome from Yellow to make him that way, the fact remains Mayday is a YX dog, and likewise Yellow was a YX dog.. In other words, Mayday and his daddy Yellow weren't just "Y" dogs, they were YX dogs, and that 'X' is coming from their respective mamas, is it not? I think the X is being falsely omitted in the mind's eye, just because the dog is a male. What needs to be remembered is any male is a YX, and any female is XX, which means the "X" influence of the dam is still clearly present in the pups, regardless of the sex. In other words, just because Mayday is a male doesn't mean he lost his mama's influence, it just means his daddy's Y (rather than his daddy's X) chromosome obtained, but Mayday's mama's X is still present in the YX Mayday regardless. (This same truth applies to Yellow and Miss Jocko.)

In fact, if it really is true that the sire's Y chromosome only offers 32% genetic influence, while the dam's X chromosome offers 68% genetic influence, then according to this X Factor theory Mayday would actually be more influenced by his mama's genes (if Yellow's 'Y' isn't carrying the same weight as Dolly's 'X'), and Yellow would be more influenced by Miss Jock's genes as well.

Now, regarding these alleged percentages, I admit to being confused as to how they add up. If X chromosomes carry 68% of the information, I understand how it all add-up to 100% if the X is paired with a 32% Y, but what happens when two 68% X chromosomes obtain to produce a female? I mean a 68% and a 68% contribution from each side would add up to 136%, which of course is impossible. So, unless I am missing something (and I may well be!) each chromosome has to contribute only 50% - 50% from each parent, to add-up to 100%, regardless if it's an X or a Y.

Now let’s do the same analysis using Dragon Lady as an example a full belly sister to Mayday. Dragon Lady is a female expressed as XX chromosomes.
Now Dragon Lady is a female and is made of 2 X chromosomes (XX). The X received from Dolly (Follow red color) is the only chromosome she could have received as Dolly itself is a female with only 2 X chromosomes.
Now let’s look at the top of the pedigree. Dragon Lady received the other X chromosome from her sire Gr. Ch. Yellow Male (YX). Gr. Ch. Yellow received that X from Miss Jocko. Now the question is Has Dragon Lady received any genetic information from Gr. Ch. Yellow John? According to the X Factor theory the answer is NO.

I understand the thinking which prompted the theory, but to my way of interpreting this there seem to be three false premises being made. Before I get into them, I would like to point out that Hollingsworth's Dolly was a red/rednose, and yet DragonLady was a buckskin/blacknose which coloration she had to get from Yellow. Dragon Lady could not possibly have gotten her black nose from the rednosed Dolly. This brings us to the three major errors that are being made with this theory, which IMO are:

• 1) The idea that all of the genes are linked to the Y chromosome (I believe this is false);
  2) The idea that if the 'Y' chromosome gets passed to the pup from the sire ... and a male pup obtains ... that somehow the genetic 'X' influence of the dam is lost (I believe this is false); and
  3) The idea that if the 'X' chromosome gets passed to the pup from the sire ... and a female pup obtains ... that somehow the entire genetic influence of the sire is lost, just because he didn't throw a Y (I believe this is false).

It is my belief that the male's genetic influence is always passed on (whether he passes his Y or his X chromosome, it's still his genes), and I further believe that the female's genes are always passed on via her "X" contribution. I think which influence is the greatest is more of a "roll of the dice," genetically, but the influence of both is always there to some degree.

If you follow the colors you can understand how to apply the X Factor theory when you are evaluating a male and when evaluating a female. I strongly believe in applying this to all the breeding’s I do when selecting a male and a female to cross.

Hmm, well, again this theory actually can't explain Dragon Lady's color. If there was absolutely no genetic influence to Dragon Lady from Yellow (by virtue of Dragon Lady being an "XX" bitch), then DL should be a red/rednose like her mama Dolly. To my way of thinking, the very fact that DragonLady was a buckskin/blacknose proves Yellow's genetic influence, by way of his passed X chromosome, for it would be genetically-impossible for Dolly to have thrown a buckskin/blacknose gene, when she herself is a red/rednose animal. Therefore, the idea that all of the "genetic information" that dogs receive is absolutely linked to the sex chromosomes can't possibly be true. While Yellow may not have thrown a Y chromosome to Dragon Lady, he nonetheless did throw his genetic influence with the X chromosome he passed on to her.

This approach will change the way you look at peds. It will give you a better perspective of the contributions that females brings to the breeding and will help you understand which individuals are actually contributing to the genetic characteristics of each individual.
Hope it helps more than it confuse.

Well, the theory definitely made me think more, and it did make me rub my chin a bit, but (unless I am misunderstanding something), the way I interpret the theory would give me the opposite conclusion. Namely, if the Y chromosome only carries 32% of the sire's genetic coding, and if the X chromosome carries 68% of the dam's genetic coding, then Gr Ch Mayday would actually be 68% influenced by his mama (and only 32% influenced by his sire). However, I am still unclear as to whether it is an actual fact that the Y chromosome only throws 32% of the sire's make-up.

I also personally believe there is more of a genetic "roll of the dice" going on than these absolutely strict 32% / 68% (or 50% / 50%) numbers reflect. For example, 5 out of 7 pups may strongly resemble (and carry the traits of) the stud dog, regardless of their sexes, while maybe 2 carry the traits (and the looks of) the bitch. Like flipping a coin, "in theory" the results are supposed to be 50-50%, but in actual practice you may get 7 straight "heads" or 7 straight "tails" when you actually flip that coin. And so it is with breeding dogs IMO. In theory, the male contributes 50%, and so does the female, but in actual practice 5 pups may totally favor the male, while only 2 favor the female. And then there is the issue of "throwbacks!"

In closing, I think this is a great topic for debate and consideration. And while I personally don't subscribe to it, I do see the logic that created it, but I believe there are some faulty premises to the theory which make it unsound. (At least as I interpret it, but I may have made a mistake of my own somewhere.)

If you have any rebuttals or corrections to where I may have made an error in calculation, I certainly would like to hear it!

Thanks again for the great topic,

Jack

[StoneCity]

Jack,

Thanks for reading the article and challenge the theory. I will try to address each challenge to the best of my abilities. Remember that must studies have been made in Horses and just recently they started doing the sames studies in canines.

My opening thought is to seek clarification if it is an actual fact that the Y chromosome carries less genetic information from the sire than if he passed the X, or is this too just a theory?

That is a fact. It is larger thus carries more information.

"The X-chromosome is considerably larger than the Y-chromosome in size and Y-chromosome carries lesser inheritable materials. Different mammals have different sized X- and Y-chromosomes. For instance, the X-chromosome in a horse is 70% larger than the Y-chromosome. Canine X-chromosome’s size is 139 Mb* which is the largest chromosome among the 39 chromosome pairs. As the Y-chromosome’s size is just 27 Mb, the canine X-chromosome is over 80% larger than the Y-chromosome."

Okay, I completely follow you here, as far as the sex of Mayday goes; however what I find myself doubting is the idea that all of the genetic traits are tied in to the sex chromosome (or, should I say, are lost in the absence of a Y chromosome).

Remember that the X factor theory relates to particular traits transmitted in the X factor and FROM WHO are they getting the information from.

"According to different chromosomes, a region of DNA, e.g., quantitative trait locus (QTL) can be found that is related to a particular phenotypic trait. X-chromosomes have been shown to carry genes in relation to sex, reproduction, mental functions, muscle and a part of skeletal traits."

Okay, here is where I disagree with this theory: While Mayday is clearly a male, and while he clearly got his 'Y' chromosome from Yellow to make him that way, the fact remains Mayday is a YX dog, and likewise Yellow was a YX dog.. In other words, Mayday and his daddy Yellow weren't just "Y" dogs, they were YX dogs, and that 'X' is coming from their respective mamas, is it not? I think the X is being falsely omitted in the mind's eye, just because the dog is a male. What needs to be remembered is any male is a YX, and any female is XX, which means the "X" influence of the dam is still clearly present in the pups, regardless of the sex. In other words, just because Mayday is a male doesn't mean he lost his mama's influence, it just means his daddy's Y (rather than his daddy's X) chromosome obtained, but Mayday's mama's X is still present in the YX Mayday regardless. (This same truth applies to Yellow and Miss Jocko.)

The point here is that Mayday is a male YX and he got his Y from Yellow and his X from Dolly. That means two things:

The Information on his Y chromosome comes from Yellow and all the male ascendants. However, The Y chromosome in Mayday does not have any genetic information from Yazoo Cody who is the sire of Dolly who is the Dam of Mayday. Now in the X chromosome found in Mayday was given to him by Dolly which means he does not carry any information from Miss Jocko.

In the case of Dragon Lady she is a female XX and she got the one X from Yellow and one X from Dolly. This means:

Males determine the sex.

The X Dragon Lady received from Gr. Ch. Yellow has no genetic information from Yellow John. Why? Because for Gr. Ch. Yellow to become a male he received the Y chromosome from Yellow John and we already know that Gr. Ch. Yellow gave his X chromosome to Dragon Lady NOT THE Y.

The X Factor is a guide to follow a path regarding the pass down on genetic information. In the case of Dragon Lady even thou she is a grand daughter of Yellow John on top, she is not carrying genetic information from him.

In terms of the percentages, when it is YX, the Y brings 27 mb and X brings 139 mb or 16%/84%. When it is XX, it is 50%/50% as both X are the same size.

In terms of dominants, recesive genes, it continues to be the same rule regardless.

That is the basics for the X Theory.

[Bojacc357]

Background on DNA

Animals have two types of DNA, nuclear (nDNA) and mitochondrial (mtDNA). Nuclear DNA is found in the nucleus of a cell. The genes coded for by nDNA are responsible for external characteristics and for behavior, but they also have important regulatory functions inside the cells. Mitochondrial DNA is separate and distinct from nDNA and is found in the mitochondria of the cell. The gene coding here is strictly regulatory and has little effect on external characteristics or behavior in comparison to nDNA.

Nuclear DNA occurs in the cell as tightly packed units called chromosomes and each cell has two copies of each chromosome. One pair of chromosomes are involved in sex-determination and are, therefore, called sex chromosomes; females have two X chromosomes and males have an X and a Y. The other chromosomes are called autosomes. All mammals have only one pair of sex chromosomes, but the number of autosomes varies according to species.

Genes are discrete pieces of DNA on the chromosomes that code for particular gene products, which are proteins. Slightly different forms of the same gene are referred to as alleles and each chromosome pair has two alleles; some alleles are dominant and are always expressed, while others are recessive and are only expressed when both alleles of a gene are recessive.

It is a myth that female (or male) genetics are stronger. Certain forms of genes (alleles) are dominant and these are expressed over recessive alleles, but dominant alleles do not occur in a higher frequency in males or females. However, there are sex-linked genes (e.g., male pattern baldness in humans) and these recessive alleles--slightly different forms of the same gene--occur in nDNA, specifically on the X chromosome. Though we know much about sex-linked genes in humans, I personally know of no such studies that have been done on canids.

If you know of any new research that has been conducted on canid genetics or have anything to offer/counter, please reply or send via e-mail to me at Gwragedd Annwn as I would be interested in reading any scientific papers or hearing any comments.

[Bojacc357]

.
How is DNA Inherited?

Mitochondrial DNA comes solely from the female parent; the egg carries mitochondria as there is no room in the part of the sperm that fuses with the egg at fertilization. Here are a couple of examples to clarify how DNA is passed from parent to offspring:

A female pure wolf breeds with a pure male dog--the pups will all have the wolf mtDNA of the mother. There will be a half-and-half mixing of dog and wolf nuclear DNA. The male pups will have a pure dog Y chromosome and a pure wolf X chromosome, with all genes of the latter being expressed. The female pups would have an X chromosome from the mother (wolf) and an X chromosome from the father (dog) and the genes on these two X chromosomes will "compete" with each other, with dominant alleles being expressed and recessive being suppressed.
A female pure dog breeds with a pure wolf male--the pups will have the dog mtDNA of the mother while the nuclear DNA of the parents would again mix. The male pups will have a pure wolf Y chromosome and a pure dog X chromosome, with all the genes therein being expressed. The female pups will have an X chromosome from the female (dog) and an X from the male (wolf) and the genes on these 2 X chromosomes will "compete" with each other (dominant being expressed and recessive being suppressed).
A female wolfdog breeds with a male wolf/wolfdog/dog (it doesn't matter)--the pups would ALWAYS have the mitochondria from the mother and could never have both dog and wolf mitochondria. There will be a mixing of nuclear DNA, but the mtDNA will always remain pure dog or wolf depending on the mothers and the mothers' mothers and so on. To simplify, mtDNA is matriarchal. The nuclear DNA would mix as indicated in the two examples above.
It is important to bear in mind two things with regard to what has been said: (1) that the terms "wolf gene" and "dog gene" were used for simplicity rather than actually being two separate and distinct genes; and (2) that mtDNA is regulatory and is NOT coding for looks or temperament. When a wolf and a dog mate, the outcome as far as looks are concerned is a crap shoot. The DNA to look at in this case would be nuclear DNA, not mtDNA.

[Bojacc357]

Though it says female genetic are not stronger I can see how it's possible to thinks so. I mean if the chromosomes DNA is equal but the mitochondria DNA is only in females than she has a great influence overall. Also I did read the X Chromosome is larger. Still, reading this it does seem the female has more influence.

[StoneCity]

Here is more detail information about the X Factor and studies results. Here is one address with info http://www.utopialands.com/xfactorbreeding.htm
There are various sites where you can get information. Just search for "X Factor Breeding". This studies started with horses and proved certain traits and characteristics were transmitted by the female. Now some studies had been done in canines with very similar conclusions. Pay special attention to the conclusions of the M Factor.

X-Factor Breeding



“THE X FACTOR points out the brood bitch may be more important than previously realized.” – Another Puzzle piece, Patricia Craige, 1998

Thoroughbred breeding has made a great impact in canine breeding because of the revolutionary and exciting new insights gained by the genetics experts in thoroughbreds. In 1997, Patricia Craige published a well-known canine breeding book “Born to Win – Breed to Succeed”. Mrs Craige can be called a pioneer with the introduction of the thoroughbred’s X-Factor theory into the Canine world.

Canines have 39 chromosome pairs. Like most mammals, canines have one pair of sex chromosomes in each cell. Each sire carries one Y-chromosome and one X-chromosome, denoted as XY, while each dam carries two X-chromosomes, denoted as XX. The sire receives the X-chromosome from his dam and then passes on it to his daughters while he inherits the Y-chromosome from his sire and then passes it on to his sons. The X-chromosome is considerably larger than the Y-chromosome in size and Y-chromosome carries lesser inheritable materials. Different mammals have different sized X- and Y-chromosomes. For instance, the X-chromosome in a horse is 70% larger than the Y-chromosome. Canine X-chromosome’s size is 139 Mb* which is the largest chromosome among the 39 chromosome pairs. As the Y-chromosome’s size is just 27 Mb, the canine X-chromosome is over 80% larger than the Y-chromosome.

Different mammals' chromosomes carry different inheritable materials. For instance, the X-chromosome of the horse carries large heart characteristics. According to different chromosomes, a region of DNA, e.g., quantitative trait locus (QTL) can be found that is related to a particular phenotypic trait. X-chromosomes have been shown to carry genes in relation to sex, reproduction, mental functions, muscle and a part of skeletal traits.

As mentioned above, the X-chromosome contains the genes associated with reproduction, mental function, skeletal muscle and a part of the skeleton characteristics. The sire carries only one X chromosome while the dam carries two. Following careful breeding plans, the quality brood bitches in the breed can usually carry two quality X-chromosomes and when a brood bitch carries on two quality X-chromosomes, she can possibly produce the same quality male and female offspring. Hence, selecting a quality dam is very important.

When a breeder chooses a dam for breeding, the breeder must select a well-constructed bitch with a good producing record. When selecting a stud dog for breeding, the breeder must study the structure and the reproductive record of the stud dog’s dam. In order to produce good brood bitches in the breeding program, the breeder should only use the stud dogs that are produced by great dams since the X of the sire will be passed onto his daughters. In this respect, mediocre bitches must be avoided in the breeding programs.

Referring to figure 2.1, Venus must contain one of Vanna’s X-Chromosomes and she has a 50% chance to carry Jordan’s X-chromosome and a 50% chance to carry one of two Marilyn’s X-chromosomes.

Parents


2nd Generation


3rd Generation

TITUS XY




CHIEF XY


FROSTY

ERLENE

VANNA XX


JOE

SISKA

PIXIE XX OR XX


JORDAN XY


SPECS

Maggie

Marilyn XX


Chief

SPREE

Figure 2.1. Venus’s pedigree

Just like every other breeding methodology, the X-factor also has its limitations. Breeders need to be aware of the sex linked diseases, which is an abnormal gene contained in the X chromosome. Normally, sex linked diseases are linked with X-chromosome. It is extremely rare for sex linked diseases to be contained in the Y-chromosome. For example, XL-PRA disease is linked with the X-chromosome in the Siberian Husky.

*Chromosome size in Mb based on bivariate flow cytometry measurements

M-Factor



While both muscle and structure are important to provide support and movement to the dogs, the metabolic system also has equal importance in relation to movement. Its chemical reaction, which occurs in all living organisms generates energy and maintains life. Due to the extremely heterogeneous tissue of the mammalian skeletal muscle, its different muscle fibres can metabolically satisfy various functional demands. The Siberian Husky is an example of this. The Siberian Husky is required to have an explosive movement to start, which is provided by Type II (fast twitch) muscle fibre, and endurance, which is provided by Type I (slow twitch) muscle fibre.

Mitochondria are structures within cells that convert the energy from food into a form that cells can use. The number of Mitochondrion depends on the biochemical metabolic level. The more exuberant the metabolic activities are, the more mitochondria there are present in the cell. Mitochondria can be described as "cellular power plants" because its organic matter oxidation can convert energy into Adenosine triphosphate (ATP). Mitochondria have a small amount of their own DNA, which is called as mitochondrial DNA (mtDNA). mtDNA contains thirty-seven genes, which are essential to normal mitochondrial function.

Oxidative phosphorylation is defined as the process of using oxygen and sugars to create the main energy source of the cell, which is ATP. In order to make enzymes in oxidative phosphorylation, instructions are given by thirteen of mtDNA genes. The more a muscle is capable of oxidizing organic matter into ATP, the better the muscle will be.

M-Factor, so called by thoroughbred breeding theorist Ken McLean, refers to mtDNA. Biologists also discovered the following three points in regards to Mitochondria:

1) They possess their own DNA with its slightly different genetic code. mtDNA is independent and non-Mendelian.

2) Mitochondria can only be passed onto the next generation by the mother. She can pass on some of her mitochondria in the cytoplasm of the egg.

3) The rate of evolution of mtDNA appears to be approximately ten times faster than that of Nuclear DNA (i.e. DNA found in the nucleus of cells.

In reproduction, since mitochondria are inherited only from the dam, the dam’s egg cell will destroy the mitochondria in mammalian sperm after fertilization.

Ken McLean believes that in racing horse breeding, superior mitochondria can be transmitted via direct female line for generations. “Perhaps some race horses inherit far superior mitochondria from their dams in direct female-line descent. This might explain why some families can produce a consistent number of stakes winners.”, he wrote in Genetic Heritage.

What does M-Factor have done with canine breeding? Because the sire cannot pass on mtDNA to his offspring, it is essential that breeders select a dam with a correct musculoskeletal system. When breeders apply X-factor theory and understand the importance of M-factor in breeding, they can begin to structure the pedigree and phenotype together in the hope of obtaining a quality brood bitch for their future breeding programs.

[kingkong1]

VERY NICE POSTING STONECITY !!!! IVE DONE ALOT OF RESEARCH ON THE X-FACTOR PRINCIPLE AN DO FEEL IT HAS ACCURATE ASSESSMENTS IN BREEDING PROGRAMS.WE ALL KNOW THAT THIS HOUNDS JUST DONT BREED TRUE LIKE (ex.GAMEFOWL).IVE HAD GREAT SUCCESS USING THE X-FACTOR METHOD AND WILL CONTINUE TO DO SO AND WILL RECORD MY RESULTS AFTER THE CULLING,TESTING AND PERCENTAGES ARE TALLIED.
THANKS STEWCOLE KENNELS

[StoneCity]

Happy to hear that someone else is also applying the X factor when breeding.

It will be great to tally all observations and see the results.

Best Luck!

[Bojacc357]

It makes plenty sense looking at it.