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DNA, RNA, Chromosomes, and Genes

Chromosomes

What organisms have the least and most number of chromosomes—and some in between?

Ophioglossum reticulatum, a species of fern also known as Adders-tongue, has the largest number of chromosomes with more than 1,260 (630 pairs). To date, the organism with the least number of chromosomes is the male Australian ant, Myrmecia pilosula, with one chromosome per cell (male ants are generally haploid—that is, they have half the number of normal chromosomes while the female ant has two chromosomes per cell). Another contender is bacteria that have one circular chromosome consisting of DNA and associated proteins. Some of the more common plants and animals also have different numbers of chromosomes: Humans (Homo sapiens sapiens) have forty-six; dogs (Canis lupus familiaris) have seventy-eight; cats (Felis catus) have thirty-eight; a mouse (Mus musculus) has forty; a fruit fly (Drosophila melanogaster) has eight; a mosquito (Aedes aegypti) has six; a potato (Solanum tuberosum) has forty-eight; and yeast (Saccharomyces cerevisiae) has thirty-two.



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