MARCO HERNANDEZ has given his permission for me to post the following on my dogblog. It is a very good explanation of the hairless situation/mutation. He has given an English translation. Thank you, Marco.
When we hear the word mutation, our mind make us think about abnormal, horrible beings. However, altough, certainly not in such a spectacular way, mutations form pat of every living being´s normal life, even more, we all are mutants, how can this occur???
DNA is the molecule of heredity. Each time that a being repoduces or a cell multiplies in our tissues, Dna copies are created. This molecule can be described as a code or sequence, represented by letters: G, C, T. A. Every three letters a significant unit appears, thus we could have the following sequence:
GGG-CCC-AAA-TTT hence, when Dna is copied, the ideal thing is to get the same sequence…but reality is that due to many factors such as transcription errors, radiations (even sun radiation), chemical substances….or many others..sometimes instea of getting the same sequence you get a variation. It happens every day, it happens in our bodies, right now, this is happening.
So it is that a sequence like: GGG-CCC-AAA-TTT can suddnly be transformed into: GGG-CCA-AAA-TTT This is a mutation.
This small errors in the sequences, (which in reality are huge of thousands and thousands of units, not only four as shown in the example) can be compared with errors in writing.One letter can be exchanged, a period is missing, a coma is missing, order of letters is inverted and so on….Most of the times these small changes are irrelevant (this does not mean that mutation did not occur, though)…but sometimes these changes can produce different meanings ina word, sentence or even whole paragraphs!!! Same thing happens wih DNA mutations..some times the changes are indetectable,sometimes they change details or sometimes they produce great changes in the organisms. In fact every sonle being including us are mutants due to these small changes in our individual DNA. Of course, recombination during reproduction is the way all of this is transmitted through generations. Every organism is a mutant, except clones..and this is the genetical variability of a gene pool.
As said before, some mutatios are minimal, other are quite obvious….independently from the magnitude of the changes, some mutations are good and others are adverse to the organism. Here it is that natural selection appears and the result is evoultion. Organisms with good mutations will thrive over those with adverse changes, according to the environmental requirements.
Long ago, somewhere in Mexico, a coated dog, namely an itzcuintli bitch whelped a number of hairless puppies. This was because of a mutation resulting in ectodermic displasia a condition that produces lack of hair and small incomplete teeth. Regarding nudity, the xoloitzcuintle is not product of progressive evolution. Instead, a mutation with very notorious effects occurred. It happened suddenly. This event couls happen once or amny times within te itzcuintli population. This is because a given population of organism do present some parts of DNA sequence more prone to similar changes. It has been since then, that due to the specific characteristics of this particular mutation that litters have been mixed (hairless and coated). This is a necessary biological condition and it is unchangeable. Duality in these dogs will always exist. Furthermore, it was the coated dog the one that originated the hairless variation and also, it is the coated the genetically pure form of the breed…hairless xolo is a mutation affecting part of the original coated-itzcuintli population. It is not an essentially different thing. In fact, coateds and hairless, altough different in a single mutant gene, share the incredibly huge DNA sequence. Their genes are exactly the same. This also goes for peruvian hairless dog an chinese crested breeds.
The sudden way this mutation appeared let us to state that some beliefs about xolo nutrition are essentially incorrect. Some people believe that the xolo lost their teeth gradually as a result of progressive evoution towards a vegetarian diet. It is highly possible indeed, that itzcuintlis and xolos were fed with many vegetal food and that they had to adapt to this diet by selective evolution. Even like this, the lack of teeth in xolos does not reflect this. Xolos still today are omnivorous canines and they do need animal matter in their diet.
One example that illustrates as possibl the sudden mutations event in canines is the documented case of the american hairless terrier. Among a regular population of these terriers, one day a hairless litter appeared. Working with these puppies a new breed was established. howevr it is important to state that this mutation in the terriers is another, different mutation that the one that the other hairless breed have (xolos, peruvian, chinese crested). A different part of the DNA sequence mutated creating a similar effect. In fact hairless terriers have small hairs creating a surface similar to touch to that of a peach, Also the terrie mutation does not affect dentition.
Gracias por leer, Thanks for reading,