Which type of genetic cross involves only one trait, example RR x rr?

A genetic cross that involves only one trait is identified as a monohybrid cross. In this type of cross, two individuals that differ in a single trait are mated to observe the inheritance patterns of that trait. The example given, RR x rr, represents a monohybrid cross where one parent is homozygous dominant for the trait (RR) and the other is homozygous recessive (rr). This setup allows for the study of the segregation and assortment of alleles, ultimately leading to the F1 generation which in this case would all exhibit the dominant phenotype.

Understanding monohybrid crosses is fundamental to genetics, as it demonstrates how traits are inherited according to Mendelian principles. The ratios observed in the offspring help to predict and understand inheritance patterns. In this instance, the offspring produced from the cross would showcase a dominant phenotype in a 100% ratio, revealing that when one parent carries both dominant alleles, those traits will be expressed in the offspring.