Information Available from the F1 and F1 reciprocal progeny - Autosomal Inheritance

In many diploid organisms, traits can be classified as autosomal or sex-linked.  The terms autosomal and sex-linked refer to the type of chromosomes that carry the genes. (inactive link ) Chromosomes are distinguished by their size, shape, banding patterns and secondary constrictions (inactive link ).  In diploid organisms, chromosomes come in pairs that look identical under a light microscope. These homomorphic chromosomes have the same size, shape, banding patterns and secondary constrictions (same shape = homomorphic).  Males and females have the same sets of homomorphic chromosomes.  In humans, for example, there are 22 different autosomal pairs present in both males and females.  The seven traits studied by Mendel were autosomal.

In many organisms there is another pair of chromosomes, the heteromorphic chromosomes, that have different shapes.  These chromosomes are involved in sex determination.  From the genetic point of view, sex chromosomes modify the Mendelian ratios that were derived from autosomal genes. Each modification of Mendelian ratios depends on the inheritance and on the type of sex-determination.

The table below summaries the phenotypic patterns that you expect to see in the F1 and F1 reciprocal progeny assuming autosomal inheritance.

The F1 and F1 reciprocal crosses are an unknown, homozygous mutant mated to a homozygous wildtype individual.

Let A1 be the mutant allele and A2 be the wildtype allele for an autosomal gene, The F1 and reciprocal F1 crosses are shown below.

 

 

Dominance of Mutant Allele

 Autosomal
Recessive Phenotype
  1. The F1 and F1 reciprocal crosses give the same results.
  2. The F1 progeny (male and female) are all phenotypically wildtype.
 Dominant Phenotype
  1. The F1 and F1 reciprocal crosses give the same result.
  2. The F1 progeny (male and female) are all phenotypically mutant.
Incompletely Dominant Phenotype
  1. The F1 and F1 reciprocal crosses give the same results.
  2. The F1 progeny (male and female) have a phenotype that is intermediate to the parental phenotypes.
Overdominant Phenotype
  1. The F1 and F1 reciprocal crosses give the same results.
  2. The F1 progeny (male and female) show a phenotype that is more extreme than either of the parental phenotypes.
 
Codominant Phenotype
  1. The F1 and F1 reciprocal crosses give the same results.
  2. The F1 progeny (male and female) show both parental phenotypes, simultaneously.

 

F1 crosses
1 F1 cross -definition
2 Information Available from the F1 and F1 reciprocal progeny. 
4 F1  Autosomal Inheritance
4 F1  X - Linkage
5 F1  Z-Linkage
6 Summary Dominance Patterns for Autosomal & Sex-Linkage.
6. Home