Which symbols (genotypes) are involved in the cross to produce the f2 generation of roan cattle?

Rr × Rr

Explanation:

Gregor Mendel, the father of Genetics, performed several experiments that led to the principles that govern heredity. He discovered that; an organism receives two forms of a gene called ALLELE, from each parent. According to his law of dominance, he also discovered that an allele is capable of masking another for a particular trait. He called the allele that masks or is expressed DOMINANT allele while the allele that is masked RECESSIVE allele. But in exception to this rule, genetic scenarios have occured.

For example, in cattles, where the allele for red hair (R) is not dominant or recessive to the allele for white hair (r), instead, they are both and equally expressed in the offspring. This genetic scenario is called CO-DOMINANCE.

In cattles, purebred red cattles (RR) i.e. homozygous or having identical alleles crossed with purebred white cattle (rr) i.e. also homozygous, will result in F1 Roan cattles (Rr), which is an hybrid or heterozygote i.e. combination of two different alleles. The roan cattle expresses both the phenotype of the parents i.e. possesses both red and white hairs.

To get the F2 offsprings/generation, the F1 offsprings are self crossed i.e. the hybrids are crossed together Rr × Rr.