Plant genetics
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Plant genetics is the study of genes, genetic variation, and heredity specifically in plants.[1][2] It is generally considered a field of biology and botany, but intersects frequently with many other life sciences and is strongly linked with the study of information systems. Plant genetics is similar in many ways to animal genetics but differs in a few key areas.
The discoverer of genetics was Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring. He observed that organisms (most famously pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene. Much of Mendel's work with plants still forms the basis for modern plant genetics.
Plants, like all known organisms, use DNA to pass on their traits. Animal genetics often focuses on parentage and lineage, but this can sometimes be difficult in plant genetics due to the fact that plants can, unlike most animals, be
The study of plant genetics has major economic impacts: many staple crops are genetically modified to increase yields, confer pest and disease resistance, provide resistance to herbicides, or to increase their nutritional value.
History
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The earliest evidence of plant
In the early 1900s, botanists and statisticians began to examine the segregation ratios put forth by Mendel. W.E. Castle discovered that while individual traits may segregate and change over time with selection, that when selection is stopped and environmental effects are taken into account, the genetic ratio stops changing and reach a sort of stasis, the foundation of
For a more thorough exploration of the history of population genetics, see History of Population Genetics by Bob Allard.
Around this same time, genetic and plant breeding experiments in
While breeding experiments were taking place, other scientists such as Nikolai Vavilov[12] and Charles M. Rick were interested in wild progenitor species of modern crop plants. Botanists between the 1920s and 1960s often would travel to regions of high plant diversity and seek out wild species that had given rise to domesticated species after selection. Determining how crops changed over time with selection was initially based on morphological features. It developed over time to chromosomal analysis, then genetic marker analysis, and eventual genomic analysis. Identifying traits and their underlying genetics allowed for transferring useful genes and the traits they controlled from either wild or mutant plants to crop plants. Understanding and manipulating of plant genetics was in its heyday during the Green Revolution brought about by Norman Borlaug. During this time, the molecule of heredity, DNA, was also discovered, which allowed scientists to actually examine and manipulate genetic information directly.
DNA
Geneticists, including plant geneticists, use this sequence of DNA to their advantage to better find and understand the role of different genes within a given genome. Through research and plant breeding, manipulation of different plant genes and loci encoded by the DNA sequence of the plant chromosomes by various methods can be done to produce different or desired genotypes that result in different or desired phenotypes.[13]
Meiosis
During plant
Plant Specific Genetics
Plants, like all other known living organisms, pass on their traits using
Some plant species are capable of
Plants are generally more capable of surviving, and indeed flourishing, as
Model organisms
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Arabidopsis thaliana
Arabidopsis thaliana, also known as thale cress, has been the model organism for the study of plant genetics. As Drosophila, a species of fruit fly, was to the understanding of early genetics, so has been A. thaliana to the understanding of plant genetics. It was the first plant to ever have its genome sequenced in the year 2000. It has a small genome, making the initial sequencing more attainable. It has a genome size of 125 Mbp that encodes about 25,000 genes.[19] Because an incredible amount of research has been done on the plant, a database called The Arabidopsis Information Resource (TAIR) has been established as a repository for multiple data sets and information on the species. Information housed in TAIR include the complete genome sequence along with gene structure, gene product information, gene expression, DNA and seed stocks, genome maps, genetic and physical markers, publications, and information about the A. thaliana research community.[20] Many natural inbred accessions of A. thaliana (often referred to as "ecotypes") are available and have been useful in genetic research. This natural variation has been used to identify loci important in both biotic and abiotic stress resistance.[21]
Brachypodium distachyon
Nicotiana benthamiana
Nicotiana benthamiana is a popular model organism for both plant-pathogen and transgenic studies. Because its broad leaves are easily transiently transformed with Agrobacterium tumefaciens, it is used to study both the expression of pathogen genes introduced into a plant or test new genetic cassette effects.
Other model plants
Other models include the alga Chlamydomonas reinhardtii, the moss Physcomitrella patens, the clover Medicago truncatula, Antirrhinum majus (snapdragon), the C4 grass Setaria viridis, and maize (corn).
Genetically modified crops
Genetically modified (GM) foods are produced from organisms that have had changes introduced into their DNA using the methods of genetic engineering. Genetic engineering techniques allow for the introduction of new traits as well as greater control over traits than previous methods such as selective breeding and mutation breeding.[22]
Genetically modifying plants is an important economic activity: in 2017, 89% of corn, 94% of soybeans, and 91% of cotton produced in the US were from genetically modified strains.[23] Since the introduction of GM crops, yields have increased by 22%, and profits have increased to farmers, especially in the developing world, by 68%. An important side effect of GM crops has been decreased land requirements,[24]
Commercial sale of genetically modified foods began in 1994, when
There is a scientific consensus[29][30][31][32] that currently available food derived from GM crops poses no greater risk to human health than conventional food,[33][34][35][36][37] but that each GM food needs to be tested on a case-by-case basis before introduction.[38][39] Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe.[40][41][42][43] The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation.[44][45][46][47] There are still ongoing public concerns related to food safety, regulation, labeling, environmental impact, research methods, and the fact that some GM seeds are subject to intellectual property rights owned by corporations.[48]
Modern ways to genetically modify plants
Genetic modification has been the cause for much research into modern plant genetics, and has also led to the sequencing of many plant genomes. Today there are two predominant procedures of transforming genes in organisms: the "Gene gun" method and the Agrobacterium method.
"Gene gun" method
The gene gun method is also referred to as "biolistics" (ballistics using biological components). This technique is used for in vivo (within a living organism) transformation and has been especially useful in monocot species like corn and rice. This approach literally shoots genes into plant cells and plant cell chloroplasts. DNA is coated onto small particles of gold or tungsten approximately two micrometers in diameter. The particles are placed in a vacuum chamber and the plant tissue to be engineered is placed below the chamber. The particles are propelled at high velocity using a short pulse of high pressure helium gas, and hit a fine mesh baffle placed above the tissue while the DNA coating continues into any target cell or tissue.
Agrobacterium method
Transformation via
See also
- Apomixis
- Biological engineering
- Biotechnology
- Cloning
- DuPont
- Eugenics
- Experimental evolution
- Gene flow
- Gene pool
- Genetic erosion
- Genetic pollution
- Genetically modified organisms
- Human genetic engineering
- Ice-minus bacteria
- List of emerging technologies
- Marker assisted selection
- Monsanto Company
- Paratransgenesis
- Recombinant DNA
- Research ethics
- Synthetic biology
- Transgene
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