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3n, 4n, 8n. What do they mean?

This is a discussion on 3n, 4n, 8n. What do they mean? within the New Growers: Ask the Senior Members forums, part of the New Growers category; I have seen some orchids being sold as "8n", "4n". What does they really mean? ...

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  1. #1
    blrnut is offline Senior Member
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    Question 3n, 4n, 8n. What do they mean?

    I have seen some orchids being sold as "8n", "4n". What does they really mean? How does an
    "orchid xyz" differ from "orchid xyz '4n'"?

    Satish

  2. #2
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    In normal reproduction, the sex cells are haploid (n) meaning the offspring gets half the set of one parent and half the set of the other.
    In plants you can have a full set of those sex cells passed on, they're called diploid (2n) gametes.
    So say you have an ovary full of diploid egg cells (2n) and a regular haploid(n) sperm cell, the result will be offsprings with one full
    set of chromosomes from one parent and half the set from the other.
    It's called triploid (3n).
    Triploids have usually larger flowers, good growth, number of flowers can be increased but they are usually sterile and cannot be used reliably for breeding.
    So now if you have an egg cell that is diploid (2n) that encounters a sperm cell that is diploid (2n) you get a tetraploid (4n).
    Tetraploids produce larger flowers with great shape that last longer, the plant can adapt to a wider range of growing conditions, the plant is overall stronger.
    That's kind of a general answer but I am sure you get the idea.

  3. #3
    mtequine's Avatar
    mtequine is offline Senior Member
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    General answer? Well, I'm impressed, where were you when I was teaching high school biology?
    Posted via Mobile Device

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    Lizgeo is offline Senior Member
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    Quote Originally Posted by Lambert View Post
    In normal reproduction, the sex cells are haploid (n) meaning the offspring gets half the set of one parent and half the set of the other.
    In plants you can have a full set of those sex cells passed on, they're called diploid (2n) gametes.
    So say you have an ovary full of diploid egg cells (2n) and a regular haploid(n) sperm cell, the result will be offsprings with one full
    set of chromosomes from one parent and half the set from the other.
    It's called triploid (3n).
    Triploids have usually larger flowers, good growth, number of flowers can be increased but they are usually sterile and cannot be used reliably for breeding.
    So now if you have an egg cell that is diploid (2n) that encounters a sperm cell that is diploid (2n) you get a tetraploid (4n).
    Tetraploids produce larger flowers with great shape that last longer, the plant can adapt to a wider range of growing conditions, the plant is overall stronger.
    That's kind of a general answer but I am sure you get the idea.
    Thanks for the explanation. Learning something new everyday

  5. #5
    Ron-NY is offline rothaholic
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    8n...have never seen that
    Laurent good explanation!

    I would like to add that colchicine is chemical that is used to treat yet undifferentiated cells to to inhibit mitosis (the splitting of the cell's DNA prior to reproduction of the cell) therefore you end up getting cells with double the number of chromosomes...4n (tetraploid) instead of the normal 2n (diploid).

    In meiosis the division of sex cells into haploid cells (1n cells) If the plant's cells are 4N...you will get sex cells that are 2n instead (diploid)

    So if you mate a normal plant the sex cells are 1n with a polyploid plant whoes sex cells (pollen or egg cells) are 2n you end up with a plants that have an extra set of chromosomes so they are triploid (3n). The same goes for mating 2 polyploid plants together with each parent contributing 2n you will end up with baby plants that are 4N.

    I assume one could treat a 4n plant to stop mitosis and get cells that are 8n but I have not noted any of these...that is not saying that there are not any.

    In general this is called polyploidy

  6. #6
    Brutal_Dreamer's Avatar
    Brutal_Dreamer is offline Dreaming with my eyes open...
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    Nice going, guys!

    Cheers,
    BD

    Quote Originally Posted by Lambert View Post
    In normal reproduction, the sex cells are haploid (n) meaning the offspring gets half the set of one parent and half the set of the other.
    In plants you can have a full set of those sex cells passed on, they're called diploid (2n) gametes.
    So say you have an ovary full of diploid egg cells (2n) and a regular haploid(n) sperm cell, the result will be offsprings with one full
    set of chromosomes from one parent and half the set from the other.
    It's called triploid (3n).
    Triploids have usually larger flowers, good growth, number of flowers can be increased but they are usually sterile and cannot be used reliably for breeding.
    So now if you have an egg cell that is diploid (2n) that encounters a sperm cell that is diploid (2n) you get a tetraploid (4n).
    Tetraploids produce larger flowers with great shape that last longer, the plant can adapt to a wider range of growing conditions, the plant is overall stronger.
    That's kind of a general answer but I am sure you get the idea.
    Quote Originally Posted by Ron-NY View Post
    8n...have never seen that
    Laurent good explanation!

    I would like to add that colchicine is chemical that is used to treat yet undifferentiated cells to to inhibit mitosis (the splitting of the cell's DNA prior to reproduction of the cell) therefore you end up getting cells with double the number of chromosomes...4n (tetraploid) instead of the normal 2n (diploid).

    In meiosis the division of sex cells into haploid cells (1n cells) If the plant's cells are 4N...you will get sex cells that are 2n instead (diploid)

    So if you mate a normal plant the sex cells are 1n with a polyploid plant whoes sex cells (pollen or egg cells) are 2n you end up with a plants that have an extra set of chromosomes so they are triploid (3n). The same goes for mating 2 polyploid plants together with each parent contributing 2n you will end up with baby plants that are 4N.

    I assume one could treat a 4n plant to stop mitosis and get cells that are 8n but I have not noted any of these...that is not saying that there are not any.

    In general this is called polyploidy

  7. #7
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    Mabuhay!

    Wow, thanks for the information, and i thank God that it didn't make my nosebleed. hehehe And I thank you also for satishsherikar for asking the question coz it has been like forever lingering in my mind what those numbers are, i guess, i just didn''t pay any attention to it.

    Just a follow-up question, does this apply to all orchids?

    thanks in advance for any response
    Last edited by mujacko2002; December 2nd, 2009 at 11:34 PM.

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    Thanks, Laurent and Ron!

  9. #9
    Kailash is offline Junior Member
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    This principle is applicable to all living cells - not only orchids.

    Basically, each cell has the capacity to multiply. The process of multiplication is called cell division. In lower organisms like bacteria and some fungi, the process is extremely simple and corresponds roughly with 1 of the methods in us humans. Mitosis and Meosis are the two methods of cell division in humans as well as in plants including orchids. While mitosis occurs in all cells of the body for maintaining the growth,etc., Meosis or reductional division occurs only in specialized GERM CELLS which are concerned with reproduction - by producing specialized cells called gametes. During fertilization, these gametes fuse to form a ZYGOTE which is a single cell from which the entire organism grows.

    The 'n' used in all these descriptions refers to basically a "HAPLOID" number - that is the basic number of set of chromosomes. Chromosomes are nothing but the genetic material in the form of DNA complexed with a large set of proteins. It is visible only during a particular phase of cell division after treatment with static drugs including colchicine and many more. In humans and mostly almost all other living organisms, the normal number of chromosome sets is a DIPLOID number or 2n. Any variation from these usual normal number of sets is called ANEUPLOIDY and includes TRIPLOIDY, POLYPLOIDY, etc.

    In plants, however, due to various reasons - both natural as well as human induced, these number of chromosome sets in the individual cells is as high as 16n. The genetic material or DNA - collectively called the "GENOTYPE" codes for numerous proteins, enzymes and other components that together interact, are complexed together to give the final physical form or the "PHENOTYPE" of that organism. So in cases of plants, the more the number of copies of the genes, the greater they're expressed thus greater protein build-up and thus you get better varieties. This is the basic idea behind Bio-engineering of genetically altered vegetables and stuff. In case of orchids, I presume (have not read any specific data or information - but based on what I understand), that as the number of chromosome sets is increased in aneuploid varieties like 3n, 4n, 8n, etc., the net protein expression is also increased - thus you get better looking flowers, better quality and the sort. However, this is not necessarily true always because a lot of times, these aneuploids are not viable or capable of surviving and rather than being more better varieties actually turn out the exact opposite.

    Hope this is helpful.

  10. #10
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    Thanks, Kailash!

    Cheers,
    BD

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