Crossbreeding and cubing

[BristledOne]

Hi Everyone!In a recent topic (2014 price guide) I saw mention from squiggle about Phenotypes and Genotypes. I hope he doesn't mind me quoting him on this as I feel it's probably the best description I've read in a while

genotype(genetically pure) & phenotype(looking like but impure genetics)

This then started some talk about what counts as pure? and how some genetics skip generations. It got my mind-a-jogging and so below I'd like to write up some of my thoughts on genetic purity and the explanation of these skipping genetics and how they come to be. I'd really appreciate everyone's input, as we all know I'm only new to shrimp keeping but I have been searching into these things before when trying to figure out how line bred guppies came to be and more recently I did the maths to figure out plans for my longfin Bristlenose projects."Cubing" and line breedingThe principal should be able to apply to any sort of genetics, fish, birds, dogs and...people 0_0But pretty much it's just keeping the mother or father, breeding it with a suitable mate then crossing back the children with the parent you most want them to match. So for shrimp we tend to accept you keep the male as it can be bred to more shrimp in a shorter period of time, but you can technically do it by keeping a chosen female and crossing her back with her male young but you will get less offspring in a given space of time and those offspring all have a chance of expressing slightly different phenotypes. So the more phenotypes we can choose from the greater chance we have of selecting and strengthening desired traits along the way. This is how traits such as longer or unusual fins on fish like guppies have been found and secured, same goes I imagine with the CRS shrimp as I believe they originally were a rare color morph found coming from CBS, then someone isolated that trait through cube line breedingBelow is what I believe to be correct maths for the cubing process, the aim is to show how many generations to get to a rough percent of the desired genetics, in this case represented as a TB as that's what spurred the talk. After 7 generations you'll break into 99% original parent DNA, second gen you are past 75% and that's why you'll start to see an increase in the numbers of TB phenotypes occurring, I'm not sure but I believe the TB traits to be recessive (like albinism) which would explain why typically at 50% TB genetics you wont see many TB phenotypes expressed100% (TB) + 0% divided by 2 = 50%100% (TB) + 50% divided by 2 = 75%100% (TB) + 75% divided by 2 = 87.5%100% (TB) + 87.5% divided by 2 = 93.75%100% (TB) + 93.75% divided by 2 = 96.875%100% (TB) + 96.875% divided by 2 = 98.437%100% (TB) + 98.437% divided by 2 = 99.2185%I hope this is at least partially correct, would be embarrasing if I'm completely on the wrong track. But if not well I hope this helps some people get an idea at just how pure the F4 TBM's or whatever it is you are looking at are.Goodluck and happy breeding!-BristledOne

[Daydream]

Good thread.The point I was trying to make was once the line is contaminated it will never be pure.And that people can only guarantee for the generations that they have personally produced .Have breed fish this way for at least 20 years and had great results.Now I am moving my efforts to my shrimp.Was also making the point that A shrimp is only worth what someone is willing to pay.There are some good breeders here that strive on securing their bloodlines and strengthening the desired traits so we all can enjoy them.

[BristledOne]

Definately agree with you, as we can see here once you taint a bloodline the numbers will rarely get back to 100% pure. In Australia especially we dont get to call many of our shrimp "pure" only pure for the time we keep them, we know that we cant import PRL's for example that's why stunning breeders like Squiggles and Bluebolts do what they can to secure and strengthen the bloodlines that are already within our waters. It takes time, effort, skill and patience to get some of these bloodlines to where they are. Sadly it takes little to no effort at all to ruin them again if the wrong person gets them. Was hoping that these numbers can be used to back up points like yours, at the end of the day you often get what you pay for and these F2, F3's out there are no where near pure

[Daydream]

Problem being that some people get into it because they think of making a quick buck with little to no effort on quality.Find that after 12 to 48 months they have burnt their bridges by suppling poor quality stock or ripping people off.Then leaving the hobby but by then the damage is done.This happens in every animal keeping hobby not just ours.Love that you put the % chart up.Hope it helps a lot of members understand what,how and why thing happen in their tanks.

[clipper]

Interesting topic, and interesting maths on the gene transfer maths. I'm curious to know what species or reproduction model you are basing this on, as shrimp gene transfer or any animal that has small generation intervals with many young have much lower input of gene transmission then human to human reproduction for example. Either way its good to see people considering the genetics of their bloodlines.

[BristledOne]

As far as I know without DNA testing you can never tell the exact % of genetics transferred, whether shrimp, people or plants. If you have information about whether the female or male passes on the most genetics though that would be an interesting read for sure!

as far as what model I've based its not catered to a specific species it's just maths based on the assumption that the male and female each provide an equal 50% towards the offspring, but that 50% doesn't necessarily visual show it's just being carried.

But for now as best as I can tell your F1's should throw out the widest range of phenotypes (again keep in mind some traits are dominant) as it's got a wider mix of genetics but as you cube back to the parent each successive generation should imitate the parent more and more and the recessive traits start to emerge more or become refined)