Breeding question

[kennyman]

I was reading the Fry Notation under the BAP panel heading and had a question about F1 offspring. How does the grading effect fry when the same parent is bred to various batches of offspring?

As an example. Two tankrasied fish are bred to produce F1 fry and then a selected female of that batch is bred back to the original male. Does the result = F2. And if the a selected female of the F2 batch is bred back to the original male does the resulting fry =F3 still? 

[darkdep]

Good Question.  I THINK your hypothesis would be correct (i.e breeding offspring back to the original male = F2) but Mseguin can probably confirm.

[mseguin]

If I remember correctly from Genetics, while it wouldn't quite be F2, the inbreeding coefficient would be the same since you are as related to a sibling as you are to either parent. I think.

[kennyman]

Seeing I have kept only one male, if I wanted to practice responsible breeding I would have to discard all my females except the original ones after the third generation reaches sexual maturity?

[mseguin]

Well with only one male, ur not going to have much in the way of variance, what you would want to do is breed males from the second generation instead of breeding back to the original male

[kennyman]

I was eliminating all other males before they had a chance to breed in an effort to reduce the effects of inbreeding but if I understand this discussion so far then the rules of inbreeding would still apply to any F3 females allowed to reach sexual maturity in my tank?

[mseguin]

No you'd be better off breeding siblings together rather than breeding back to parents.
Think of it in terms of one loci (one point on the chromosome). Let's say that loci codes for fin colour. Now let's say the father is homozygous (both copies of the gene are the same) for red fins, whereas the mother is heterozygous (one copy codes for red, the other for say yellow) for red. Their offspring will either be homozygous or heterozygous for red fins, and all will have red fins (assume red is dominant). If you were to breed one of the offspring to the father, you would always get red fins, since his genes would alwyas be dominant. (which you would want if ur trying to create a pure strain). However, if u were to breed two of the heterozygous offspring, you would get a mix of offspring, although red would be the majority. Basically, by breeding back to the male, you're reducing the female's contribution to the genetics of the offspring and creating a genetic bottleneck, faster than otherwise. After a number of generations, effects like copying errors and such will start to build up, which is why u dont want to linebreed too far.
Dunno if that makes sense, if anyone thinks that its wrong or too simplistic let me know, its quite possible.

[Woody]

Matt - you are right on the mark with your comments.

There are a number of factors that have not been considered to give a true answer. For starters what species and if you are trying to line breed for a certain characteristic.
Certain species are more prone to heredity problems than others, take for example the Goodied family. most of the ones in captivity are the off springs of a single amle and female rescued from the enviroment and 30 years later, the species thrives in captivity with no heredity problems.

If you are looking to fix a certain trait or characteristics the offspring are bred back to the male to fix those traits then crossed further down the line but that is another subject.

Is this question general or does it involve a specific species?

Woody

[kennyman]

The fish I am breeding is a form of Pseudotropheus elongatus. But as more general answers come I am learing about future endeavors as well.