Silkworms
dominant gene: yellow cocoon (c)
recessive gene: white cocoon (c)
parents: cc x cc
1. genotype:
2. phenotype:

Genotype of the offspring: 4 CC is equal ratio.  Phenotype will be 4 yellow cocoons. (CC)

Explanation:

The inheritance of cocoon color in silkworm is a classic illustration of mono-hybrid cross. Mono-hybrid because the color of cocoon is determined by single gene. The yellow color of cocoon is dominant and the homozygous dominant allele is represented as CC. While the white color of cocoon is represented as cc homozygous recessive alleles. As per punnett square method the offspring cocoon color will follow the above mentioned genotypic and phenotypic ratios respectively.

50% lit on the left side