inheritance of brain size (interpretation of diallel crosses)

Richard Gordon gordonr at cc.UManitoba.CA
Thu May 18 23:42:57 EST 1995

Dear Gillian and Guy,
Brain size is probably a direct result of the trajectory of the ectoderm 
contraction wave. Thus a more direct approach to your problem would be to 
analyze this wave in embryos of different sexes and genotypes, to look 
for factors affecting the trajectory. See:

Brodland, G. W., R. Gordon, M. J. Scott, N. K. Bjorklund, K. B. Luchka, 
C. C. Martin, C. Matuga, M. Globus, S. Vethamany-Globus & D. Shu (1993). 
Furrowing surface contraction wave coincident with primary neural 
induction in amphibian embryos. J. Morph. 219, 131-142.

Gordon, R., N. K. Bjorklund & P. D. Nieuwkoop (1994). Dialogue on 
embryonic induction and differentiation waves. Int. Rev. Cytol. 150, 373-420.

Best regards, -Dick Gordon, U.Manitoba[May18,95]

On Wed, 17 May 1995, Guy F. Barbato wrote:

> We are currently analyzing a series of experiments intended to elucidate the 
> genetic architecture of brain size in chickens.  The data sets are comprised 
> of 4 diallel crosses made up of related and unrelated 
> populations of chickens (3, 4 and 5 parental stocks with brain and body 
> weights measured at hatch through 84 days of age in both sexes).
> During analysis of the data, using both the Griffing and Eberhart and Gardner 
> models (similar to Gene Eisen's work in mice), we also performed the 
> 'traditional' Hayman's analysis (similar to Norm Henderson's work, also in 
> mice).  We have found evidence for significant dominance for brain size using 
> both types of analysis.
> Curiously, we have observed that the expression of dominance differs between 
> males and females.  females tend to exhibit sig. dominance variation at early 
> ages which diminishes over time, while males exhibit increasing dominance at 
> later ages.
> Does anyone have any thoughts regarding possible genetic or evolutionary 
> explanations of differential expression of dominance between the sexes??
> please respond to me or to Gillian Leach (grl104 at email.psu.edu)
> thanks,
> guy
> ====================================================
>  ////         G. F. Barbato                Phone: (814)-865-4481
> < * )         Dept. Poultry Science        FAX:   (814)-865-5691
>   \ \__///    Penn State University        Lab:   (814)-865-3189
>   ( --- )     University Park, PA 16802    Email: gfb1 at psu.edu
>    \/ \/        **** URL: http://ps235.cas.psu.edu/ ****
> ====================================================
>      A non-secular nanosecond of thought:
>             " Education is what survives when
>                  what was learnt has been forgotten."
>                                  --------  B.F. Skinner

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