What is the probability that a gamete from an Rr parent carries an r allele?

In a parent with the genotype Rr, there are two types of gametes produced: those carrying the R allele and those carrying the r allele. The probability of a gamete carrying the r allele is 1 out of 2 possible gametes (R or r). Thus, the probability that a gamete from an Rr parent carries the r allele is 50%, or 0.5.