Genetic Architectures

Dairy cattle eventually graduate to McDonalds, so there is some interest in the genetics of beef production in dairy breeds.  There is course more interest in the genetics of beef production in beef breeds of cattle.

Usually you don’t find a single allele that makes a lot of difference, but in some beef breeds, there are myostatin mutations that result in a ridiculous-looking, ‘double-muscled’ beast. Homozygosity for myostatin mutations causes difficulties in birth, so it takes really strong selection for  beef production to make a myostatin null common.  I  don’t think you ever see this in dairy breeds.

But, as it turns out, there is a deletion that is pretty common in some dairy breeds that significantly increases milk production while killing homozygotes before birth.

Breeds under weaker selection for single traits, your typical cow of the past, probably have neither.

The point is that the genetic architecture of a  quantitative trait does not have to be the same in different populations of the same species.  For example, I have the impression that height is not as highly polygenic in Pygmies as it is most other human populations. There’s a particular region on chromosome 3 that seems to influence height- you don’t see such a concentration in Europeans.

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15 Responses to Genetic Architectures

  1. Sandgroper says:

    Probably totally irrelevantly, I was entertained recently watching a programme about these things: http://en.wikipedia.org/wiki/Dexter_cattle

    They’re now breeding them in numbers in Northern Ireland for beef production – they thrive in poor country that won’t support much else. Apparently the flavour is very gamey, and the more hill climbing on their little legs that they have to do, the gamier they taste.

    • gcochran9 says:

      see next post – I’d like to have your input.

    • Paul Conroy says:

      Dexter Cattle are a dwarf breed of Kerry Cattle, which in turn are directly related to the ancient, small, black, Celtic cattle – such as the Welsh Black and the Aberdeen Angus… and I would add the Camargue Cattle to this list…

      They were positively selected for, as even a relatively poor family – a family of 10-15 people living on a few acres – in the 1700/1800’s could afford one. In those times, the poor didn’t much/any meat, most protein came from milk.

      http://www.ansi.okstate.edu/breeds/cattle/dexter/
      http://www.ansi.okstate.edu/breeds/cattle/kerry/

      • Sandgroper says:

        I’m sorry, Paul, this is the wrong sort of cow, and the wrong sort of Gaelic, but Julie Fowlis is married to an Irishman. I hope you enjoy it, anyway.

      • Paul Conroy says:

        Sandy,

        Interesting…

        I wonder has anyone ever done a study on autosomal DNA of Highland Cattle and compared them to Yaks? While it’s unlikely they are related, and more likely that their similar adaptions to high altitude is an example of parallel evolution, nevertheless it would be interesting to know for sure …

  2. beancrusher says:

    So, this is not the point, but as a dairyman I am curious and feel like I should know…what is the deletion in dairy breeds you reference?

  3. AllenM says:

    Here is a good discussion of breeding genetics by a working ranch: http://www.bartbar.com/articles.html

    Now, they make money doing this:

    “Bull selection is probably significantly more important over the longer term,” Teichert says. “In the short term, I think heifer selection is more important, especially if you let Mother Nature do some of the testing for you. Don’t over-develop heifers and let those that will get pregnant in a short season (30 days or less) get pregnant…Those heifers bred in a short season end up being better cows and staying that way.”

    Along with the ability to conceive in a short season, Teichert looks for reasons to eliminate them from the herd rather than for justification to keep them. For him, reasons to eliminate include heifers with sub-par performance, any hint of eyes problems, feet and leg problems, poor disposition, heifers too tall or too narrow.

    “You need to set objectives for what works on your ranch and in your environment,” Teichert says. “If you raise your own replacements, the bulls you select become the future of your herd. Meanwhile, judicious cow culling can clean up your herd and make it more manageable and marketable.”

    If you applied this criteria to humans, the howls would be immense, yet that is exactly what we are doing.

    Humans, a free range long term genetic experiment.

  4. rob says:

    It’s not only the genetic architecture of trait that can differ between populations. The trait-trait covariations could differ between populations.

  5. I thought the pygmy-masai height discrepancy was largely life histiry acceleration rather than genes per se?

  6. Greying Wanderer says:

    milk – best food ever

  7. Pingback: linkfest – 03/21/14 | hbd* chick

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