To solve this problem, we need to analyze the given statements:$\newline \bullet$Statement I: Chromosomes become gradually visible under light microscope during leptotene stage.$\newline$ - During the leptotene stage of prophase I in meiosis, chromosomes start to condense and become visible under a light microscope.$\newline$ - This is the first stage of prophase I where the chromatin begins to condense into visible threads.$\newline$ - Hence, Statement I is true.$\newline \bullet$Statement II: The beginning of diplotene stage is recognized by dissolution of synaptonemal complex.$\newline$