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WHAT IS SEX-LINKED DOMINANT

INHERITANCE IN BIRDS?

Sex-linked genes are located only on the sex-chromosomes. Sex-linked dominant means that the gene for a dominant factor in a bird is located on the sex-chromosome. A sex-linked dominant gene is visible even when present only in one sex-chromosome. Females have only one sex-chromosome (X-). Males have two sex-chromosomes (XX). In females, if they have the sex-linked gene, it will be visible, as they have only one sex-chromosome to which the sex-linked gene is on. In males, the sex-linked gene is visible even when present only in one sex- chromosome. That means, a male is be visible for the dominant factor when it is single-factor or double-factor. I. e. the factor Agate in canaries is sex-linked recessive, but also sex-linked dominant to Isabel. If a canary male carries both factors (Agate + Isabel) it is visible for Agate and split for Isabel. Females never can be split for a sex-linked gene.   Here are some mating examples: X = Sex-Chromosome, also called        X-Chromosome F = Factor (dominant)
MALE (FX)
F E M A L E
F
X
X
F
X
X
F
X
X
MALE (FF)
F E M A L E
F
X
F
F
X
F
X
F
F
MALE (FX)
F E M A L E
F
X
F
F
F
X
F
F
X
MALE (FF)
F E M A L E
F
F
F
F
F
F
F
F
F
Male: double-factor = visible for the dominant factor Female: without the dominant factor Results:  50 % males, single-factor = visible for the dominant factor and split for another recessive factor (FX) 50 % females, single-factor = visible for the dominant factor (F-)
Male: single-factor = visible for the dominant factor and split for another recessive factor Female: without the dominant factor Results:     25 % males, single-factor = visible for the dominant factor and split for another recessive factor (FX) 25 % males, without the dominant factor (XX) 25 % females, single-factor = visible for the dominant factor (F-) 25 % females, without the dominant factor (X-)
Male: double-factor = visible for the dominant factor Female: single-factor = visible for the dominant factor Results:  50 % males, double-factor = visible for the dominant factor (FF) 50 % females, single-factor = visible for the dominant factor (F-)
(X-)
(F-)
(F-)
(X-)
Male: single-factor = visible for the dominant factor and split for another recessive factor Female: single factor  = visible for the dominant factor Results:  25 % males, double-factor and visible for the dominant factor (FF) 25 % males, single-factor = visible for the dominant factor and split for another recessive factor (FX)                                     25 % females, single-factor = visible for the dominant factor (F-) 25 % females, without the dominant factor (X-)                   
MALE (XX)
F E M A L E
X
X
F
F
F
X
X
X
X
Male: without the dominant factor Female: single factor = visible for the factor dominant Results:  50 % males, single-factor = visible for the dominant factor and split for another recessive factor (FX) 50 % females, without the dominant factor (X-)                   
(F-)