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A plant genome is the sequence of DNA that provides the information for a plant to live. Within all living organisms, the genome is made up of the genetic material for that organism. The DNA molecules are grouped into genes that provide the instructions that determine what a plant does, its color, shape and size, where and how it grows, etc. Every living organism has a genome that is made up of all of its genes that determine what that organism is.
Every genome, including a plant genome, is made up of a string of nucleotides that form the DNA of that organism. There are four types of nucleotides found within DNA, which are alanine (A), thymine (T), guanine (G) and cytosine(C). The strings of nucleotides can be very long, and their order is what makes up the genes. Instead of one long strand of DNA, the genes are grouped on chromosomes that are found within the nucleus of every cell of the organism. As well as having different genes, different species of organism also have different numbers of chromosomes.
Studying genomes has been carried out by scientists for many years. Geneticists have been trying to find the genes that code for particular traits and functions of living things. Until recently, they have been limited in what they can find, but they have now developed methods or finding the entire sequence of nucleotides that make up a genome. To sequence a plant genome, the scientist has to determine every nucleotide that is found in each chromosome of the plant that is being studied.
Determining the sequences of plant genomes has not been easy due to the wide range of plants, as well as the great difference in their genomes. The range of plant genome sizes varies from species that have genomes that are as small as those of small animals to other plants that have genomes that are almost forty times the size of the human genome. The very first plant genome to be completely sequenced was the Arabidopsis plant, which is a small cress plant that is part of the mustard family. This plant was chosen as it has a relatively short genome when compared to other plants. Sequencing of the Arabidopsis genome found that it has 25,000 genes, which are now used to help determine the genomic sequence of plants that have much longer and much more complex genomes.