Genetics Maize

exotic varieties of maize collected add genetic diversity when selectively breeding new domestic strains

many forms of maize used food, classified various subspecies related amount of starch each has:

flour corn: zea mays var. amylacea
popcorn: zea mays var. everta
dent corn : zea mays var. indentata
flint corn: zea mays var. indurata
sweet corn: zea mays var. saccharata , zea mays var. rugosa
waxy corn: zea mays var. ceratina
amylomaize: zea mays
pod corn: zea mays var. tunicata larrañaga ex a. st. hil.
striped maize: zea mays var. japonica

this system has been replaced (though not entirely displaced) on last 60 years multivariable classifications based on ever more data. agronomic data supplemented botanical traits robust initial classification, genetic, cytological, protein , dna evidence added. now, categories forms (little used), races, racial complexes, , branches.

maize diploid 20 chromosomes (n=10). combined length of chromosomes 1500 cm. of maize chromosomes have known chromosomal knobs : highly repetitive heterochromatic domains stain darkly. individual knobs polymorphic among strains of both maize , teosinte.

barbara mcclintock used these knob markers validate transposon theory of jumping genes , won 1983 nobel prize in physiology or medicine. maize still important model organism genetics , developmental biology today.

the maize genetics cooperation stock center, funded usda agricultural research service , located in department of crop sciences @ university of illinois @ urbana-champaign, stock center of maize mutants. total collection has 80,000 samples. bulk of collection consists of several hundred named genes, plus additional gene combinations , other heritable variants. there 1000 chromosomal aberrations (e.g., translocations , inversions) , stocks abnormal chromosome numbers (e.g., tetraploids). genetic data describing maize mutant stocks myriad other data maize genetics can accessed @ maizegdb, maize genetics , genomics database.

in 2005, national science foundation (nsf), department of agriculture (usda) , department of energy (doe) formed consortium sequence b73 maize genome. resulting dna sequence data deposited genbank, public repository genome-sequence data. sequences , genome annotations have been made available throughout project s lifetime @ project s official site.

primary sequencing of maize genome completed in 2008. on november 20, 2009, consortium published results of sequencing effort in science. genome, 85% of composed of transposons, found contain 32,540 genes (by comparison, human genome contains 2.9 billion bases , 26,000 genes). of maize genome has been duplicated , reshuffled helitrons—group of rolling circle transposons.