Information Available from the B1 progeny - Autosomal Inheritance

  The B1 backcross is a cross of an F1 or F1' individual to a P1 individual.  The F1 or F1' individual may be the male or the female.  These, two crosses will give the same progeny genotypes. The expected B21genotypes for a single autosomal gene are given below.

B1 Backcross - Autosomal Traits

For a single autosomal gene, the B1 backcrosses give the same genotypes for both males and females.  One half of the genotypes will be homozygous ( the same genotype as the P1 parent) and 1/2 of the genotypes will be heterozygous (the same genotype as the  F1 or F1' parent). 

The P1 parent has Genotype A1A1.  If the A1 allele is completely dominant all of the progeny of the B1 backcross will look like the  P1 parent .  The expected results for other dominance patterns are given below.

 

Dominance of Mutant Allele

 Autosomal
 A1 allele is Dominant  All of the of the B1 progeny (male and female) have the P1 phenotype.
A1 allele is Incompletely Dominant 1/2 of the progeny B1 progeny (male and female) have the P1 phenotype and 1/2 the  B1 progeny (male and female) have a phenotype that is intermediate to the  P1 and P2 parental phenotypes.
 
A1 allele is Overdominant 1/2 of the progeny B1 progeny (male and female) have the P1 phenotype and 1/2  the  B1 progeny (male and female) have a phenotype that is more extreme than the  P1 and P2 parental phenotypes.
 
A1 allele is Codominant with A2 allele 1/2 of the progeny B1 progeny (male and female) have the P1 phenotype and 1/2 the  B1 progeny (male and female) show both the P1 and P2 parental phenotypes, simultaneously.


 

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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