# Percentage of bloodline?

Discussion in 'General breed discussions & FAQ' started by tls_ranch, Oct 13, 2011.

1. ### tls_ranchStares at Chickens

I can't seem to find the chart that talks about % of blood after outcrossing to a different breed? I saw it posted somewhere, but I can't find it now

Like:
first generation= 50% breed A, 50% breed B
second gen=75% breed A, 25% breed B
third gen=?
fourth gen=?

and on.......

Does any one have a link or can re-post it?

Thanks

Last edited: Oct 13, 2011

2. ### SvarthonaSongster

Oct 4, 2009
Couldn't find a chart either, sorry.
But the maths behind outcrossing to another breed once is, that the remaining genes will decrease by half with every new generation.

100% A X 100% B = 50% A - 50% B (breed B is contributing 1/2 to the first generation)
100% A X 50A/50B = 75% A - 25% B (breed B is contributing 1/4 to the second generation - 1 out of 4 grandparents)
100% A X 75A/25B = 87,5% A - 12,5% B (breed B is contributing 1/8 to the third generation)
100% A X 87,5A/12,5%B = 93,75% A - 6,25% B (breed B is contributing 1/16 to the fourth generation)
1/32 in the fifth generation
1/64 in the 6th generation, so with the 6th generation you are back to 98,5% "purebred" A

(Just works like this if you breed back to a 100%breed A bird every time, brotherXsister matings do not work like that.)

3. ### AquaEyesSongster

Why do you need a chart? It's math. Each generation is half of one parent plus half of the other parent.

A X B = 50% A, 50% B

A X AB = 75% A, 25% B (one parent is 100% A. Cut that in half to 50%. The other parent is 50% A and 50% B. Cut each of those in half. You'll get 50% A + 25% A + 25% B = 75% A, 25% B)

Keep going down the line.

4. ### ChickenSnakeChirping

Punnett square!! I loved that in High School

5. ### AquaEyesSongster

Quote:That was something different -- for predicting percentages of genotypes in crosses. This is about determining percentage of "line A" versus "line B" contributing genes to offspring when one line is bred in, then offspring are repeatedly bred back only with the other. So if A X B, the offspring get 50% of their genes from B. If one of those offspring is bred back to A, then the next generation gets 75% of their genes from A and 25% of their genes from B. And so on.

6. ### CattitudeSongster

I think this is the chart you're looking for:

7. ### tls_ranchStares at Chickens

Quote:Yay, thanks! Just what I was looking for I saw it some where and then I couldn't find it again

Trisha

8. ### pastorwaltChirping

Apr 26, 2011
Now let me throw a monkey wrench in the works:
If one is trying to increase the percentage of a particular breed
by using roosters of that breed on hens of an ever increasing percentage
one will never get hens with the female chromosome of the desired breed
no matter what math says. Since the female is the hetero-gamete in birds
the hens will have that chromosome from the original foundation hen
not that it probably matters

9. ### hallerlakeSongster

4,870
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May 30, 2010
Seattle
Quote:Some of us are visual learners. Charts just make more sense to me.

10. ### CattitudeSongster

Quote:If your hen has the most desirable traits, simply visualize her as the black circle instead of the white/outline. Plus, anywhere along this line, you can choose a different rooster and hen, and begin again at the top. Or bring in a non-related rooster or hen who has the traits you want. The chart is a visual aid rather than a blueprint.