Genetic linkages in
pigeons - an often misunderstood inheritance mechanism
If two genetic factors both
are located at the same chromosome, would they have to appear
'linked' again in later generations? That says the word linkage! Or
Every breeder can easily
understand that the color genes lie on the sex chromosome. The male
in pigeons has two chromosomes due to gender, the female only one.
The daughters inherit their chromosome from the father, the sons one
from the father and one from the mother. A blue pigeon (genetically
black base color) with a dilute red pigeon (ash red or dominant red
base color) produces heterozygous red cocks and blue hens.
The dilution factor is also
on the sex chromosome. A dominant yellow cock (homozygous dilute)
with a dominant red pigeon will produce heterozygous dilute red
cocks and yellow females.
The third set of experiments
affects both color and dilution. The mating of a pure-bred cock with
a black base color and a yellow hen (dominant red + dilution factor)
will result in red-colored cocks and black young females.
In the fourth test
arrangement, this heterozygous red young cock is mated to a yellow
hen. Due to the gender-specific inheritance, we know that all
youngsters with a black base color are hens. You don't need a
molecular genetic analysis or later observations of behavior. They
are shown as a group in table 28 of the book ‘Taubenzucht’ and for
the purpose of this contribution yellow marked.
Source: Taubenzucht, Achim
Eight of the 17 black
females were diluted. Black as the phenotype of the wild-type was
thus separated from the wild type at the dilution locus in eight
cases and associated with the dilution factor. The dilution and
color gene on the chromosome are apparently so far apart that there
is a break in the inheritance process and a new combination of the
genes. Eight out of 17 make a crossing over and a new combination of
47% in black base colored females.
Source: Taubenzucht, Achim
2019. Outcome for the bilateral combination of color (black and ash
red), beak length (long and short), breast frill (plain and frill)
and dilution (dilute and non-dilute). Total number of backcross of F1-cocks
to yellow Old German Owl hens 56.
To determine the overall
crossover rate also for red and yellow hens and also for cocks, the
sex of all youngsters would have to be determined by molecular
genetic studies or behavioral analyses which is not included in this
didactic demonstration. But even without this extension, the result
of the study by Cole and Kelley (1919), almost 100 years ago, is
confirmed. They found a relatively large distance and came to a
crossover rate of around 40%.
In the last test arrangement
not only the dilution and color expression are recorded, but also
the length of the beak and frill or non-frill. As with many
empirical studies, this study answers some questions, but also
Cole, L.J., and F.J. Kelley,
Studies on inheritance in pigeons. III. Descriptions and linkage
relations of two sex-linked characters. Genetics 4, 1919, pp.
Sell, A., Pigeon Genetics.
Applied Genetics in the Domestic Pigeon, Achim 2012.
Sell, A., Taubenzucht. Möglichkeiten und
Grenzen züchterischer Gestaltung, Achim 2019.