All four B1 hybrid crosses

Sex-Linked Traits   XX-XY system

Trait is completely dominant

 

 

There are four possible B1 crosses.  The progeny distributions depend on the genotypes of the mother and fathers of the cross (i.e, P1, F1 or F1').  The expected genotypic distributions of the four crosses are diagramed below. 

 

Reminder :
 

The P1 generation has genotypes A1A1 & A1Y1;   The P2 generation has genotypes A2A2 & A2Y2.  The F1 has genotypes A1A2 & A1Y2 and the F1' generation has genotypes A1A2 & A2Y1

 


 

B1 Hybrid Cross

 

 Phenotype

(P1 x F1) = A1A1 x A1Y2

Progeny

 

  

A1A1

♀

100% P1 phenotype

A1Y2

♂

100% P1 phenotype

B1' Hybrid Cross

 

 Phenotype

(F1 x P1) = A1A2 x A1Y1

  

 

 

1/2 A1A1 ; 1/2 A1A2

♀

100% P1 phenotype

1/2 A1Y1 ; 1/2 A2Y1

♂

1/2 P1; 1/2 P2 phenotypes

          B1'’ Hybrid Cross

 

 

(P1 x F1') = A1A1 x A2Y1

 

 

  

A1A2

♀

100% P1 phenotype

A1Y1

♂

100% P1 phenotype

B1'’‘ Hybrid Cross

 

 

(F1'x P1) = A1A2 x A1Y1

 

 

  

1/2 A1A1 ; 1/2 A1A2

♀

 100% P1 phenotype

1/2 A1Y1 ; 1/2 A2Y1

♂

 1/2 P1; 1/2 P2 phenotypes

 

With complete dominance, 100% of the  females always have the phenotype of the P1 parent.  In two of the four crosses (B1 & B1'’) 100% of the males have the phenotype of the P1 parent. In the other two crosses ((B1'& B1'’') 1/2 of the males have the phenotype of the P1 parent and 1/2 of the males have the phenotype of the P2 parent.

 

If the heterozygote has a unique phenotype the results are somewhat different.

B1 crosses
1 Definition
2 Single Autosomal Traits - All dominance patterns
4 Single Sex-linked Trait (XY)  - Complete Dominance dominance
4 Single Sex-linked Trait (XY)  - Other dominance patterns
5 Single Sex-linked Trait (ZW)  - All dominance patterns (inactive)
5 Two autosomal traits - unlinked genes -All dominance patterns (inactive)
6 Two autosomal traits -linked genes - All dominance patterns (inactive)
7 Some general rules for two or more genes (inactive)
8 Problems (inactive)
   
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