The eleven corn genes affecting the nature of starch synthesis in corn grains illustrates how much, and how little we know of genes in corn. Much of what we know of location and function of corn genes is based upon occurrence of mutants, such as the waxy gene affecting corn starch synthesis. Maize Genetics Cooperation Stock Center was formed in 1932 as a means of collecting unique mutants and sharing with corn genetics researchers. It is currently located at University of Illinois and can be found on internet at maizecoop.cropsci.uiuc.edu
Genetic studies using mutants has allowed some understanding of relationship of specific genes to some structures and activities in the corn plant but there remains a lot left to learn. Careful analysis of mutations through breeding methods has even allowed location of these genes not only as to on which of the 10 chromosomes of corn but in relation to other mutants. Mutant genetic studies have contributed considerably to our understanding of corn genetics and has been limited to only a few hundred genes.
Chromosomal DNA is a string of units, each of which are composed of 3 of a possible 4 nucleic acids. Most possible combinations code for one of 20 amino acids. A gene is a string of these amino acid codes that has a start nucleic acid combination not related to an amino acid and a stop combination that also does not translate to an amino acid. Actual translation of the DNA gene occurs when the section between the start and stop portion transcribed into a RNA molecule which is moved to the ribosome organelle in the cell. The codes are then translated into corresponding amino acids which are connected to each other to form very specific proteins. The arrangement and sequence of amino acids have significant effects on their enzymatic activity in biosynthesis of structure and function of the plant. A mutation may be only a single nucleic acid change in the DNA change that results in the substitution of a different amino acid in the final protein that affects the enzymatic activity.
Analysis of corn DNA of a single inbred (B73) by counting those with Start and Stop codons concluded that there were at least 32000 genes in that corn plant. We have a very limited knowledge of which ones are most significant in terms of final corn production. Surely some affect some structures and functions that are not related to grain production, at least in some environments. On the other hand, having at least 32000 genes provides plenty of opportunity to select for features that lead to successful growth of corn across many environments.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.