Секция Родезийский риджбек при МООиР

Разведение => Генетика: теория и практика => : AriesKhan August 29, 2007, 17:16:24

: Наследование риджа
: AriesKhan August 29, 2007, 17:16:24
We have just learned that the specific genetic mutation responsible for the ridge in the Rhodesian Ridgeback has been found.

The work was done by Dr. Leif Andersson at Uppsala University in Sweden in collaboration with researchers at the Broad Institute/MIT here in the U.S. and the Swedish University of Agricultural Sciences. A paper will be published in the coming months, and Dr. Andersson expects a genetic marker test to be available in the fall, pending licensure, etc.

That is all the information Dr. Andersson has given us, along with his permission to disclose it to the Ridgeback community. We know you are as thrilled as we are.

As many of you know, Dr. Mark Neff, in collaboration with RRCUS, was also searching in parallel for the same marker. While Dr. Neff's efforts were not responsible for this discovery, we all agree it is wonderful for the breed.

We are sure this will be a subject of intense interest at Dr. Bell's seminar next Wednesday at the National Specialty in Ohio, as he will be discussing the implications of a direct-marker test for breeders.


Сотрудничество шведов и американцев привело к тому, что 23 мая на семинаре в Америке на Национальной выставке в Охайо будет объявлено о точном наследовании риджа и маркеровочных тестах. способных определить носителей. И т.д.

Как и предполагалось, такой признак как ридж имеет простое аутосомное доминантное наследование - утверждает председатель секции "Генетика и Здоровье" американского Национального Клуба Denise Flaim:

The ridge gene is a simple autosmal dominant gene, comparable to black nose. It makes sense to think about this as dogs carrying the gene for the ridge, as opposed to dogs carrying for ridgelessness (which is the normal state in dogs).

The comparison to Chinese cresteds (where hairlessness is also a defining trait of the breed and also a simple dominant) is valid, but there is an important distinction: In Cresteds (and also regarding tailnesses in Manx cats), the gene is a lethal homozygous: That is, animals that inherit two copies die in utero. This is obviously not the case in Ridgebacks.

If a ridgeless Ridgeback bitch -- or a bitch of any breed -- is bred to a Ridgeback who carries two copies of the ridge gene -- that is, who is homozygous -- then ALL the resulting puppies will be ridged. The puppies will also be heterozygous -- only carrying one copy of the ridge gene -- which means that they can produce ridgeless themselves if bred to another heterozygous dog. But this describes most of the American Ridgeback population anyway.

In private emails, people have expressed concerns to me that people will use a ridge marker test to eliminate ridgeless entirely, and push the breed toward homozygosity. This is a very real fear, as in the Khoi dog population, there was a natural degree of ridgelessness, and eliminating or severely curtailing the heterozygosity of the population could have unforeseen, negative effects: Since we know the ridge is linked to dermoids, this is one concern.

That said, the pendulum might very well be balanced by those who choose to use the tool to breed ridgeless to homozygotes in order to produce all ridged litters. The science of it is very sound, but the breed-culture implications in terms of the still-strong stigma attached to ridgeless is another matter entirely.

Our breed at its core is about balance, and I think that should be applied to our breeding practices as well. The most important thing we need to maintain is breed diversity and as wide a gene pool as possible. If you eliminate dogs from breeding because they carry for undesirable traits, then you might as well spay and neuter them all, as they ALL carry for something. If nothing has expressed in your dog's progeny, that doesn't mean he or she is clear of any and all deleterious genes -- there is no such thing. It just means that you haven't seen them express ... yet.

So ... when we have tools such as genetic marker tests ... and this is only the first of what I hope will be many ... we should in principle use them whenever possible to expand the gene pool, not contract it. After all, a direct-marker test is the ultimate -- it lets you "look into" your dog's genes. It tells you exactly what is there. And it lets you, with full knowledge, predict and control the outcome.
Denise Flaim
RRCUS Health & Genetics Chair

Ген, отвечающий за проявление риджа, простой доминантный ген (сравнимый с геном локуса В, отвечающего за наследование черной мочки носа). Большинство пород не имеют риджа (гомозиготны по признаку "безриджевости"), что является нормой.
Сравнение с китайской хохлатой, где бесшерстность также наследуется простым доминантным наследованием, в принципе верно, но есть важное отличие: в хохлатках ген бесшерстности является летальным в гомозиготном состоянии. Поэтому сравнивать с риджбеком эту породу нельзя.
Люди беспокоятся, что возможность применения маркеров, определяющих носителей рецессивного гена (отсутствие риджа), устранит безриджевость и подтолкнет породу к гомозиготности по данному признаку. Это действительные опасения, т.к. можно добиться устранения гетерозиготности в популяции, что очень отрицательно скажется на породе, т.к. мы знаем, что наличие риджа связано с Дермоидным Синусом.
Очень важно поддерживать разнообразие в породе и как можно более разнообразный генотип. Маркеры, определяющие генотип, следует использовать, чтобы расширить генотип, а не сузить его...

Было добавлено, что нет точных знаний, связывающих ДС и наличие риджа. Это только предположение, что некоторые составляющие риджа, к примеру завитки, связаны с ДС (волосы закручиваются спиралью внутрь, а не вверх). Этим также объясняется и наличие этого заболевания в других породах, которые также имеют завитки (кокеры или доберы). Также можно объяснить, почему безриджевые особи имеют иногда (реже, чем риджевые) это заболевание: они могут иметь ген (ы) , отвечающие за наследование завитков, но не риджа как такового.
Однако - всё это теория.

To be clear, nobody is saying that there is a link between dermoids and homozygosity for the ridge. There is believed to be a link between dermoids and the presence of the ridge itself.

There is one school of thought that says that some component of the ridge -- perhaps the crowns -- is connected to dermoids. (What is a dermoid, after all, but a crown that spirals downward instead of upward?) This also explains why dermoids, however uncommon, have been found on breeds that occasionally have whorling (i.e. cockers and Dobes). This also explains why ridgeless can have dermoids (though it is rare): They can inherit the gene(s) for crowns, but not the ridge gene which allows them to manifest.

This is all theory, of course

: Re: Наследование риджа
: AriesKhan August 29, 2007, 17:18:01
В разделе "Племенной брак" открыта тема о случае "нестандартного" наследования риджа.