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Published byGerard Croucher Modified over 10 years ago
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USEFUL MUTANTS Heritable changes can result in a useful novel phenotype, i.e., a new allele.
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Other Kinds
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Some “not bad” Mutants
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Sweet Corn Single gene mutations in several different starch biosynthesis genes have been introduced into tender, flavorful corn to produce the sweet corn we eat today - Instead of transferring sugars into starch, they accumulate ‘sweetness’. Shrunken (Supersweet), sugary, sugary enhancer, amylose extender.
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Ornamental Corn Single gene mutations in the anthocyanin (pigment) production pathway lead to the colored kernels we see on an ear of Indian corn.
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Waxy Corn A mutation in the waxy gene is used in production of tapioca and other gelling starch products.
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High-lysine Corn A mutation in the opaque2 gene results in increased levels of the essential amino acid, lysine. Quality Protein Maize (QPM).
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o2, opaque endosperm: endosperm soft and opaque; high lysine content; regulates b-32 protein. Photo: seed from a selfed ear segregating for opaque kernels in transmitted light showing opaqueness of mutant kernels.
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And of course -- Disease resistance Insect resistance Glossy mutants Flowering time Cytoplasmic male sterility Nutritional changes “Value-added” changes
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Mutations and Co-evolution Variations usually exist in nature. Co-existing species experience mutual selection.
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Domestication by Culture Suppression of ‘Wild’ Traits Seed scattering Mixed timing Hard-shelled seeds Mutation/Selection of ‘Desired’ Traits Packaging Convenience Storability Processing
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Domestication in Wheat DIVERGENCE, CROSSING, SELECTION Earliest cultivated and wild wheat, with the 7- chromosome A genome (left), crossed with another, with the B genome, (third) about 8000 BC. The result was durum wheat (emmer = PASTA WHEAT), fourth in this photo. Emmer crossed with wild goat grass (fifth) and gave rise to the staff of life (BREAD WHEAT), sixth. The combination, AABBDD, 7x3 = 21 chromosomes, is productive and high in food quality.
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Ninetieth birthday of the Father of the Green Revolution, Nobel Peace Prize Laureate Norman Borlaug http://www.cimmyt.org/english/webp/support/news/borlaug_90.htm Dwarf Wheat Opened Doors
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New Wheats a la Nature Deliberate employment of diversity in collections. Crosses of AABB with diverse DD and others.
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http://www.maizegdb.org/cgi- bin/imagebrowser_phenotypes.cgi Mutant Images for Maize
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Ramosa tassel and ear
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Terminal ear1
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Teopod2, Tunicate1
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White pollen1 (bursting)
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Virescent1
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Directed Transposon Tagging Yellow seed have tagged si1 allele (Si1 y1/si1-mum Y1) Grow plants from yellow seed and backcross to si1 y1/si1 y1. Plant out seeds, score for silky vs normal tassel phenotype. Prepare DNA from leaves of each type. An example---cloning the male sterile silky1 (si1) gene using Mutator. si1 y1/si1 y1 X Si1 Y1/Si1 Y1, Mu-active (white seed/silky tassel) X (Yellow seed/normal tassel) Perform co-segregation analysis to identify transposon linked to your mutant phenotype. all Yellow seed (y1/Y1) si1 y1/Si1 Y1 (99.99%) Normal Phenotype si1 y1/si1-mum Y1 (rare mutant 1/10000) X Si1 y1/Si1 y1
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(normal tassel) Southern Blot Hybridized with Mu1 Probe (silky tassel (si1/si1-mum))
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M0M0 M0M0 M1M1 M1M1 bz1* sh1* C1 sh1 bz1 Lyophilized leaf disks DNA M2M2 M2M2 Random intermating Random intermating Bulk Seed Bulk Seed Minimum criteria: ≥50 M 2 seed with ≥60% germination Maize Genetics Stock Center for distribution Maize Genetics Stock Center for distribution Grow- outs open to the general public Forward screens for specific traits of interest M3M3 M3M3 EMS treat pollen TILLING = Targeting Induced Limited Lesions IN Genomes c1 Sh1 Bz1 Make mutant population
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DNA prepared and equal amounts of each sample arrayed to microtiter wells, then these 8-fold pooled IR-labeled primers create double end-labeled fragments
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IR700IR800 200 bp 95bp Bands of complementary size are visible, one in each image channel, corresponding to singly end-labeled fragments cleaved by CELI at the mutation site. Mutant individuals identified from pools, sequenced. Information and analysis returned to User, along with Stock Center numbers for ordering seed.
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