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Yellow podded white flowered pea?

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  • Jang
    commented on 's reply
    Thank you for these, Silverleaf. I’m understanding bits and look forward to your further posts/video. A video would be great!

  • Silverleaf
    commented on 's reply
    That was exactly my logic! It makes a huge difference in how many F2s I’d need to grow to be reasonably confident of seeing the phenotype I want.

  • Galina
    commented on 's reply
    Silverleaf, In your second example IF A is not an issue because you do not start with wild flowering Golden Sweet but with Opal Creek (both Opal Creek and Nightmist are a), then it also becomes a two factor cross and your chance of getting green flowers and yellow pods is 1 in 16, rather than 1 in 64. Statistically much easier to achieve.

    I can see why it makes more sense to make this cross with Opal Creek.
    Last edited by Galina; 14-04-2021, 10:42.

  • Galina
    commented on 's reply
    Thank you Silverleaf.

  • Silverleaf
    commented on 's reply
    Thank you Jan, but I’ve ordered some.

  • Silverleaf
    replied
    Also I know they look scary. They absolutely aren’t when you know what they represent, and they are much much simpler than stupid old Punnett squares.

    Leave a comment:


  • Silverleaf
    replied
    I’m planning on doing a proper post about these diagrams later, and I’ll probably also make a video explaining how I draw them.

    It’s basically a probability diagram stolen from mathematics, because if you’re trying to work out the ratios of different phenotypes it’s really just probability.

    Each “node” of the tree represents a locus and we concentrate on them one at a time - you see with the Elisabeth x Beacon cross that at the first node the plant can either be B_ (meaning it has at least one copy of B but we can’t know what the other one is - and it actually doesn’t matter) or bb. 3/4 chance of B_, 1/4 of bb.

    Then we move to the next node, where the B_ plant can either be Ce_ or cece and the bb plant can also either be Ce_ or cece. That’s four different possible phenotypes, one for each branch of the tree.

    B_ Ce_ Wild type
    B_ cece Cerise
    bb Ce_ Pink
    bb cece Light rose

    The probabilities are worked out by multiplying the fractions along the branches from the “root” to the “tip” You might remember this from school, but to do this we need to multiply the top numbers together to get the new top number, and the bottom numbers together to get the new bottom number. So 3/4 x 3/4 = 9/16 for the top branch, 3/4 x 1/4 = 3/16 for the next, and so on.

    The Golden Sweet x NightMist is the same thing but with three loci to worry about rather than two. I’ve been lazy with not writing out fractions properly and I didn’t really have space for writing out the genotypes - but I can see those from reading across the tree anyway.

    Please don’t worry if this doesn’t make sense, I’m sleep deprived and just threw this together quickly so it’s my fault! I’ll describe it better when I write it up in its own thread.

    Leave a comment:


  • Jang
    commented on 's reply
    I liked the punnet square explanation in your link, Galina. The tree diagram sounds very interesting as well. Is there any way you could send an example of one you’ve done, Silverleaf, as a photo image perhaps? Can be as rough as you like!

  • Jang
    commented on 's reply
    I have some spare Opal Creek if that would help.

  • Silverleaf
    commented on 's reply
    I think my problem is that you have to do so much work before you even start drawing a Punnett square, like working out the possible zygotes. With the tree diagram you can skip the bits that don't matter (like homozygous dominant plants being functionally identical to heterozygous plants, so you can just lump them together).

  • Galina
    commented on 's reply
    Punnett squares are so cumbersome to draw. The only way I can work with them is by using this programme. If you have no such help with only a piece of paper and a pen you can easily get the same information from the tree diagram. All based on Mendellian ratios of 3 to 1.
    https://scienceprimer.com/punnett-square-calculator

  • Silverleaf
    commented on 's reply
    Charlie’s Goldsnap does look good!

    A probability tree diagram explanation is a great idea, I hate Punnett squares with a passion and think they make everything more difficult than it needs to be.

  • Galina
    commented on 's reply
    Now that you have said the magic word - tree diagram - which has helped me understand genetic traits and what to expect and why and I still have all the examples you did that magic day, would you please write a note on it, Silverleaf? For example for this cross or for the Elisabeth x Beacon cross? Pretty please.

  • Galina
    commented on 's reply
    The white flowering Charlie's Goldsnaps that I am currently selecting out. Which to all intents and breeding purposes are similar to Opal Creek.
    Last edited by Galina; 12-04-2021, 07:47.

  • Silverleaf
    replied
    Well it took a bit of research, but it seems like Opal Creek would fit the bill nicely. Anyone know any others?

    Leave a comment:

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