Download Heredity of the Dunn-factor

Heredity of the Dunn-factor
By Hennie Pienaar
INTRODUCTION
The easiest way of describing the heredity of the Dunn-factor is through making
use of the Punnette squares.
The Punnette square works as follow:
Take for example a chequer cock (♂) with the genetic combination of Cb (a nonpurebred chequer (C) with the blue factor (b) which is recessive) and a blue bar
hen (♀) with the genetic combination of bb (purebred blue factor).
♂
Square 1 (top left) represents the
combination of the genetic factor C
(Chequer) from the cock and the genetic
factor b (Blue) of the hen. The result is Cb,
a non-purebred chequer cock or hen.
C
b
♀
b
Cb
b
♂
C
Square 2 (top right) represents the
combination of the genetic factor b (Blue)
from the cock and the genetic factor b
(Blue) of the hen. The result is bb, a nonpurebred blue bar cock or hen.
♀
b
b
bb
b
♂
Square 3 (bottom left) represents the
combination of the genetic factor C
(Chequer) from the cock and the genetic
factor b (Blue) of the hen. The result is Cb,
a non-purebred chequer cock or hen.
C
b
♀
b
Cb
b
♂
Square 4 (bottom right) represents the
combination of the genetic factor b (Blue)
from the cock and the genetic factor b
(Blue) of the hen. The result is bb, a
purebred blue bar cock or hen.
C
b
b
♀
b
bb
♂
We can summarize it as follow:
C
b
b
Cb
bb
b
Cb
bb
50% from the mating will be chequer
cocks or hens with the blue factor
recessive.
50% from this mating will be blue bar
cocks or hens (purebred for the blue
factor.)
♀
DUNN FACTOR : LINKED TO THE SEX CHROMOSONE
The factor for the Dunn factor is found (like the factor for ash red) on the same
chromosome as the sex factor. It is thus linked to the sex chromosome. The
difference between the ash red factor and the dunn factor is that ash red is a
dominant factor and the dunn is recessive.
The Punnette Squares will help as to understand it better. Remember, a cock
has two X chromosomes (XX), which not only determine the sex but also have a
lot of other genetic information. A hen has only one X chromosome and a Y
chromosome (XY). The latter is a vacant chromosome, which carries no
hereditary (genetic) information.
♂
Figure 1:
X
X
Xd
XXd
XXd
Y
XY
XY
A black factor cock (blue, chequer,
penciled or dark) is paired with a Dunn
hen, with the factor for Dunn linked to her
X-chromosome.
In the progeny:
50% will be blue bar or chequer cocks
carrying the Dunn factor recessive.
50% will be blue bar, chequer, and etc.
hens.
♀
Conclusion:
All the male progeny won’t be dunns their selves, but they will carry the dunn
factor.
All the hens of this mating won’t either be dunns or carrying the Dunn factor.
0% of the progeny will be Dunns.
♂
Figure 2:
X
Xd
X
XX
XdX
Y
XY
XdY
A blue bar, chequer, penciled or dark cock
with the Dunn factor recessive is paired
with a blue bar, chequer, etc. hen
In the progeny:
25% are cocks and will be blue bar,
chequer, etc, not carrying the Dunn factor.
25% are cocks and will carry the Dunn
factor recessive.
25% are blue bar, chequer, and etc. hens.
25% will be Dunn hens.
♀
Conclusion:
Halve of the male progeny won’t be dunns their selves, but they will carry the
dunn factor.
Halve of the male progeny won’t either be dunns their selves, or carry the dunn
factor.
Halve the hens of this mating won’t either be dunns or carrying the Dunn factor.
Halve of the hens will be Dunns.
25% of the progeny will be Dunns
♂
Figure 3:
X
Xd
Xd
XXd
XdXd
Y
XY
XdY
A blue bar, chequer, penciled or dark cock
with the Dunn factor recessive is paired
with a Dunn hen, with the factor for Dunn
linked to her X-chromosome.
In the progeny:
25% are cocks and will carry the Dunn
factor recessive.
25% are cocks and will be purebred for
the Dunn factor
25% are hens and will be blue bar,
chequer, and etc. hens.
25% will be Dunn hens.
♀
Conclusion:
Halve of the male progeny won’t be dunns their selves, but they will carry the
dunn factor.
Halve of the male progeny will be dunns.
Halve the hens of this mating won’t either be dunns or carrying the Dunn factor.
Halve of the hens will be Dunns.
50% of the progeny will be Dunns!
♂
Figure 3:
Xd
Xd
Xd
XdXd
XdXd
Y
XdY
XdY
A Dunn cock is paired with a Dunn hen,
with the factor for Dunn linked to her Xchromosome.
In the progeny:
50% are cocks and purebred for the Dunn
factor.
50% will be Dunn hens.
♀
Conclusion:
All of the male progeny will be dunns.
All of the hens will be Dunns.
100% of the progeny will be Dunns!