Where does the 1/4*V_D and 1/2*V_A come from?

Twin & family modeling
1

Hi Everyone,
In response to yesterday’s question I’ve created a video to explain where these coefficients come from:
https://www.colorado.edu/ibg/biometrical-genetics
The video is about 45 minutes but explains everything from first principles. I hope it is useful.
cheers
Dave

1 Like
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Hi Dave,

Finally had the chance to look into this after the workshop – it’s so clearly explained! I only wanted to know where the 1/4 V_D came from and I got so much more from this video lecture, so thank you very much! I especially appreciate the additional resources at the end.

Best regards,

Ralph

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Hi Ralph
So sorry to not reply to you- I’ve only looked at this forum again this year (2025!). You can think of the 1/4*V_D intuitively coming from the fact that (a) dominance effects at genotypes will only be correlated between siblings when they share the same genotype, and (b) siblings share the same genotype only 1/4 of the time. Hope this helps?!
cheers
Dave