Answer:
C
Step-by-step explanation:
The expected ratio of phenotypes in the offspring of two roan cattle can be explained by the principles of Mendelian genetics and the mechanism of incomplete dominance.
Incomplete dominance is a pattern of inheritance in which the heterozygous phenotype is intermediate between the two homozygous phenotypes. In the case of coat color in the particular breed of cattle described in this question, red is the homozygous dominant phenotype, white is the homozygous recessive phenotype, and roan is the heterozygous phenotype that results from the incomplete dominance of the red allele over the white allele.
When two roan cattle are crossed, their offspring can inherit an R allele or an r allele from each parent. If an offspring inherits two R alleles, it will have the homozygous dominant phenotype for red coat color. If an offspring inherits two r alleles, it will have the homozygous recessive phenotype for white coat color. However, if an offspring inherits one R allele and one r allele, it will have the heterozygous roan phenotype because the expression of the R allele is incomplete and is partially masked by the expression of the r allele.
Therefore, the expected ratio of phenotypes in the offspring is 1:2:1 for red:roan:white. This ratio is determined by the probabilities of inheriting different combinations of alleles from the parental generation and the incomplete dominance mechanism that governs the expression of the alleles in the heterozygous offspring.
Overall, understanding the mechanisms of incomplete dominance and Mendelian genetics is essential for predicting the outcomes of genetic crosses and understanding the inheritance patterns of traits in various organisms.