In Section $4.6 .1,$ we briefly described Sturtevant's analysis of mutant flies that culminated in the generation of the first chromosome map. In Table $4.2,$ we show the crossover data associated with the different mutations that he used to draw the map. A crossover refers to a chromosomal rearrangement in which parts of two chromosomes exchange DNA. An illustration of the process is shown in Figure $4.26 .$ The six factors looked at by Sturtevant are $\mathrm{B}$, $\mathrm{C}$, O, $P, R,$ and $M .$ Flies recessive in $B$, the black factor, have a yellow body color. Factors $C$ and $O$ are completely linked, they always go together and flies recessive in both of these factors have white eyes. A fly recessive in factor P has vermilion eyes instead of the ordinary red eyes. Finally, flies recessive in $\mathrm{R}$ have rudimentary wings and those recessive in M have miniature wings. For example, the fraction of flies that presented a crossover of the $\mathrm{B}$ and $\mathrm{P}$ factors is denoted as BP. Assume that the frequency of recombination is proportional to the distance between loci on the chromosome.
Reproduce Sturtevant's conclusions by drawing your own map using the first seven data points from Table 4.2
Keep in mind that shorter "distances" are more reliable than longer ones because the latter are more prone to double crossings. Are distances additive? For example, can you predict the distance between $\mathrm{B}$ and $\mathrm{P}$ from looking at the distances $\mathrm{B}(\mathrm{C}, \mathrm{O})$ and $(\mathrm{C}, \mathrm{O}) \mathrm{P} ?$ What is the interpretation of the two last data points from Table $4.2 ?$