5(a)Inheritance Genetic CrossesMedium4 marks
Pigeons are birds that belong to the Columbidae family. They are distributed throughout the world.
- The two sex chromosomes in female pigeons are known as the Z chromosome and the W chromosome.
- Male pigeons have two Z chromosomes.
- One of the genes controlling feather colour in pigeons is located on the Z chromosome. The W chromosome does not have this gene.
- This gene has three alleles, each coding for a different feather colour.
- The allele for ash-red feathers is dominant to the allele for blue feathers, which is dominant to the allele for brown feathers.
Using the symbols, complete Figure 5.1 to show how a cross between an ash-red male pigeon and a blue female pigeon can produce a brown offspring.
- chromosome with allele coding for ash-red colour
- chromosome with allele coding for blue colour
- chromosome with allele coding for brown colour
- = W chromosome with no gene controlling feather colour
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