![]() ![]() But a range of new techniques such as mutation induction, genetic engineering (transgenic or transformed plants), and in vitro methods ( somatic cell hybridization, tissue culture, doubled haploids, induced polyploids) expand the source and scope of variability that can be used in crop improvement. Historically, plant breeders seeking sources of variability were constrained in choice of parental materials or plant genetic resources that were interfertile through the process of recombining locally adapted plant materials via sexual reproduction within closely related gene pools or just by evaluation and selection of particular desirable, existing genotypes to produce improved plant varieties. Markers allow determination of alleles present in individuals or populations. Markers are characteristically locus-specific and polymorphic (i.e., segregating) in the population under study, and also have easily observable phenotypes. A marker may be part of a gene itself or more commonly in a chromosome segment close by a gene of interest. They can be used to track the inheritance of nearby genes to which they are closely linked. Markers can be visible traits, proteins, genes, DNA sequences, or RNA sequences, and can be genetically mapped to a particular chromosomal location. The basic tools used to characterize genetic variation within and between populations are called genetic markers. Selection is the differential reproduction of the products of recombination - both within and between chromosomes. Changes in gene frequencies within populations caused by natural selection can lead to enhanced adaptation, while changes caused by human-directed selection can facilitate development of useful genetic variability and selection of superior genotypes. Genetic variation results from differences in DNA sequences and, within a population, occurs when there is more than one allele present at a given locus. Food and Drug Administration microbiologist prepares DNA samples for gel electrophoresis analysis at the FDA lab in Atlanta. Understand underlying technologies of non-DNA marker systems and strengths and weaknesses of non-DNA versus DNA markers.Understand two basic applications of markers: fingerprinting and gene-tagging.Understand RFLP, SSR, and AFLP as examples of classical markers.Understand prerequisites, prospects, and limitations in using sequencing for genotyping.Understand nextgen sequencing bioinformatics.Understand next generation (nextgen) sequencing.Understand the importance of DNA sequence variation within species.The way that plants evolve is dependent on both genetic characteristics and the environment that they face. Evolution can be defined as a change in gene frequency over time. Evolutionary processes that alter species and populations include selection, gene flow (migration), and genetic drift – whether plants are cultivated or wild. Genetic variation – dissimilarity between individuals attributable to differences in genotype – that is generated by mutations is acted upon by various evolutionary forces. Genome mutations – involving changes in number of whole chromosomes or sets of chromosomes. Chromosome mutations are large-scale chromosome alterations including deletions, insertions, inversions, and translocations. Gene mutations involve nucleotides or short DNA segments (one or few nucleotides substituted, inserted, or deleted). Gene and chromosome mutations are discussed in this lesson. Mutations can occur at all levels of genetic organization, classified as gene, chromosome or genome mutations. Mutations are the ultimate source of all genetic variation. Thomas Lübberstedt Madan Bhattacharyya and Walter Suza ![]()
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