camille1585 |
04-16-2018 04:12 PM |
Quote:
Originally Posted by Mountaineer370
(Post 873476)
Okay, you guys. For those of us not in the know, will you tell us what 2N, 3N, 4N, etc. all mean? This is the first I've heard that kind of terminology. :blushing:
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If you go back to basic genetics, you learned that you have 2 copies of each chromosome (diploid), one inherited from your mother, and the other from your father. 1 copy of a set of chromosomes is called n (or haploid). 2 copies is 2n, 3 copies is 3n, and so on. Gamete cells are n, and the resulting offspring are then 2n (2 copies). In the case of the Sophronitis example above, the plant is naturally 2n. However, when the ploidy is doubled to 4 copies of the chromosomes (4n), the plants are usually bigger, more vigorous and produce larger flowers and fruits. Chromosomes are usually doubled artificially, by treating cells with a potent chemical that causes the chromosomes to double.
2n plants are fertile, as are 4n plants, since both a divisible by 2 (to create the gamete cells). You can breed a 2n to a 4n, with the gamete of the first giving 1 copy of the chromosomes, and the second one giving 2 copies. The resulting offspring is then 3n, and is usually sterile because the odd number prevents pairing during meiosis. Ploidy changes can also happen naturally via mutations, but it's rare.
Just for information, ploidy levels can vary A LOT between species and organisms. Potatoes are 4n, spinach is 12n, carrots are 18n, corn is 20n and some plants go as high as 300n+. In micro-organisms and animals you see the same.
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