Largest Chromosome number of Ophioglossum

I went through one picture posted randomly by someone in a social network and I found it very interesting to grab some more information about it. Human has 46 number of chromosome and you would be surprised to know about Ophioglossum, which has the highest chromosome count of any known living organism, with 1,260 chromosomes. This fern has roughly 630 pairs of chromosomes or 1260 chromosomes per cell. The fact that these cells can accurately segregate these enormous numbers of chromosomes during mitosis is truly remarkable.

O. vulgatum

O. vulgatum

Ophioglossum, which is known as adder’s-tongue and is under the family of Ophioglossum, found variedly in tropical and subtropical distribution. The name “adder’s toungue” is quite significant due to the spore bearing stalk resembles like that of snake’s tongue.

The chromosome is one of the threadlike packages of genes and other DNA in the nucleus of cells. The numbers of chromosomes vary with different kind of chromosomes. As you know already that Humans has 23pairs of chromosomes, i.e. 46 in total (normally) with 44 autosomes and two sex chromosomes. Comparing with Ophioglossum, which has 100s of chromosomes. Ophioglossum reticulatum, for example, is estimated to have from 240 to 510 chromosomes in the haploid state, or up to 1020 chromosomes in the diploid state.

chromosome

A research published in Botanical Journal of the Linnean Society, where the Chromosomal evolution of in the Ophioglossum is studied in 12 species. It is found that Ophioglossum has wide variety of chromosome numbers from n=30 in O. eliminatum to n=720 in O. reticulatum. In that report it is suggesting that “extreme selection has been exerted against the majority, and further suggesting that Ophioglossum represents an evolutionary dead end through repeated cycles of polyploidy and is possibly at the verge of extinction.”

The table of most popular organisms and their chromosome numbers

The table of most popular organisms and their chromosome numbers

Therefore, one reason adder’s-tongue ferns have so many chromosomes may be that, because they as a group appeared so early in evolutionary history, they’ve been around long enough for the polyploid-making process to have occurred several times among them.

In fact, adder’s-tongue ferns are so primitive that genetic-sequencing studies indicate that they’re not even “true ferns” — members of the taxonomic Division Pteridophyta. Instead, often they are now placed in their own division, the Ophioglossophyta.

References:

  • Genetics Review, Chromosome. NCBI
  • Ophioglossum. Wikipedia
  • Chromosome Numbers. www.web-books.com
  • SHARDA KHANDELWAL (2008). Chromosome evolution in the genus Ophioglossum L. Botanical Journal of the Linnean Society 102(3): 205-217.

Further Study:

http://www.backyardnature.net/q/ophioglo.htm

About Saumyadip

Science Communicator and article writer. ELSEVIER Student Ambassador (South Asia).
This entry was posted in Molecular Biology and Genetics and tagged , , , , , , . Bookmark the permalink.

One Response to Largest Chromosome number of Ophioglossum

  1. shaikha says:

    full of knowledge

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