To solve this problem, we need to identify who explained the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes.$\newline \bullet$T.H. Morgan:$\newline$ - Thomas Hunt Morgan was a geneticist who discovered the role of chromosomes in heredity. He is known for his work on fruit flies (Drosophila melanogaster) and linkage maps.$\newline \bullet$Gregor J. Mendel:$\newline$ - Gregor Mendel is known as the father of genetics for his foundational work on the inheritance of traits in pea plants, leading to the laws of Mendelian inheritance.$\newline \bullet$Alfred Sturtevant:$\newline$ - Alfred Sturtevant, a student of T.H. Morgan, was the first to construct a genetic map. He used the frequency of recombination between genes to measure the distance between them on a chromosome.$\newline \bullet$Sutton Boveri:$\newline$ - The Sutton-Boveri hypothesis, proposed by Walter Sutton and Theodor Boveri, suggested that chromosomes are the carriers of genetic material.$\newline$Based on the above analysis, Alfred Sturtevant is the correct answer as he explained the use of recombination frequency to map gene distances.$\newline$Therefore, the correct option is Option 3.