crocnshas wrote:G'day Tom,you are confusing yourself by saying fawn is sex linked,its not,it's autosomsal recessive.Cinnamon is sex linked,eg cinnamon diamonds,cinnamon doublebars. It becomes very confusing as these two mutations and others are called fawns,stars are another that have both cinnamon and fawn mutations and are very simmilar to look at. Craig
Except that, as per our other conversation regarding naming conventions, it still depends on who names it. Fawn longtails (so called by the original NSW breeder) are sex linked..... but hey that's another topic

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For those who do not understand what the original post is about... Cells are created in two ways:
* They divide in half, each with a full complement of genetic material, called mitosis. In mitosis the chromosome pairs line up and split in half, each 'half" becomes a new chromosome in the new cell. These are the body cells - bones, tissue, and so on - but not the sex cells (eggs and sperm).
* They divide in half, each with a half complement of genetic material, called meiosis. In meiosis the chromosome pairs line up and then the cell splits in half, each cell getting a whole chromosome but half the number, these are the "gametes" or sex cells, Put two together (one from mum, one from dad) and you have a new cell with a full complement of genetic material which divides into two, four, eight, 16, untl the new baby is fully formed. During the pairing process prior to cell division the sex chromosomes (W and Z in the case of birds) line up together, one new cell getting just one of W or Z, combining these again at fertilisation is what determines the gender of the bird.
* Sometimes when a pair lines the two chromosomes overlap, break at that overlap and re-join, we now have two chromosomes with genetic material from each. Obviously this can't happen with W and Z but can happen with two Ws. Equally, it can happen with all the other chromosomes but the results are more traceable with inherited characteristics if the controlling gene is on the sex chromosome. This overlapping, breaking and re-joining is called "crossing over" or "recombination", hence the original question in this thread.
Now, as it happens lacewing and ino in budgies appeared spontaneously many years apart and in different blood lines. As each is recessive, until (at random) this crossing over appears and puts the genes on the same chromosome at meiosis the two characteristics could not appear together as the birds will always inherit one W from mum and / or one W from dad, each containing
either a lace or an ino gene. (Now maz, I've simplified this bit, settle petal

).
Now, back to our main channel.... can't add any more to the list Ure but I'm sure others can!