The simplest explanation famous long term selection

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Unformatted text preview: top 30 are “genes of unknown function” 25 26 Artificial selection: still a viable approach? Results: Corn Oil and Protein • Despite the 43% reduction in maize diversity compared to teosinte… • Limits to artificial selection have not been reached – Can we still improve yields by imposing artificial selection? • The simplest explanation: • Famous long term selection experiment: – There are many genes affecting these traits, each of small effect – The combined effect of slight changes in allele frequency of many genes of small effect leads to the response – 100 generations of selection on corn kernels for protein and oil content Oil Content Protein Content • Conclusion: – Artificial selection will likely still work for traits with a complex genetic basis • What about traits with a different genetic basis? • Or traits for which we cannot wait 100 years for improvement? 1896! “Reversal” lines Moose et al. 2004, Trends in Plant Science 9: 359 364 28 27 -Protein content is increasing as Oil content is increasing -Reversal lines: decided to down-select and prove that the first 50years of artificial selection is responsible for implicating t hese large changes -Artificial selection will continue to work on traits that require the i nteraction of many genes to be produced Alternative approach: Use existing genetic variation and planned breeding Vitamin A deficiency • Causes eye disease in 40 million children annually • Idea: – Score all crop varieties for trait of interest – Identify genetic markers that co segregate with the trait • Places 140 250 million at risk for other Vitamin deficiency disorders Co-segregate = is associated with • Idea: • Given a robust association: – Maize is the dominant food crop in Sub Saharan Africa – Selectively breed maize to produce more vitamin A precursors – Selectively breed the genetic marker into th...
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