Final answer:
The recombination frequency in a cross between two tomato plants, where 15 out of 123 progeny are recombinant, is 12.2%, which reflects the genes' linkage and crossover frequency.
Step-by-step explanation:
The recombination frequency is calculated as the number of recombinant progeny divided by the total number of progeny. In this case, the student is dealing with a cross between two tomato plants that produced 123 progeny, 15 of which had a recombinant phenotype. To find the recombination frequency, divide 15 by 123.
The recombination frequency is 12.2%, which indicates the likelihood that crossing over will occur between the genes in question, suggesting how closely linked the genes are on the chromosome.