Small and Simple Genome

Beyond these basic traits, other attributes of Arabidopsis make it particularly well-suited for analysis by modern molecular genetic methods. Its genome (the amount of DNA in each set of chromosomes) is only about 125 million base pairs. This is small compared to many other plants, and makes searching for particular genes easier in Arabidopsis than in plants with larger genomes. For comparison, the genome sizes for rice (Oryza sativa), wheat (Triticum aestivum), and corn (Zea mays) are 420 million, 16 billion, and 2.5 billion base pairs, respectively. Furthermore, the Arabidopsis genome is contained on just five pairs of chromosomes, making it easier for geneticists to locate specific genes.

Geneticists can carry out crosses (interbreeding two different plant strains) with Arabidopsis by introducing the pollen from one plant to the stigma on another. This mode of reproduction, called outcrossing, is useful for combining mutations from different plants. Alternatively, Arabidopsis can reproduce by a process called selfing, in which an individual plant uses its own pollen to fertilize its ovules.

Selfing, which is not possible in many plants, is very useful for geneticists who wish to study mutations. Most mutations are recessive, which means that they physically manifest themselves (display a phenotype) only when they are present on the chromosomes contributed by both the ovule and the fertilizing pollen. In selfing, heterozygous mutations (which are present on only one of the two sets of chromosomes) will become homozygous (present on both) in one quarter of the progeny produced in this manner.

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