Temperature Effect on Interference and Crossing over.

A consideration of the data presented in an earlier paper (GRAUBARD 1932) brings out certain facts with regard to the mechanism of crossing over in chromosome I1 of Drosophila melanogaster which may have general significance. In the previous work experiments were performed to study crossing over and interference along the entire length of the normal chromosome I1 and of the same chromosome with a median inverted section of an estimated length of 25 units. The cross was arranged so as to have eight marked genes along the chromosome covering it from one end to the other. The genes employed were aristaless (3.0) dumpy (13.0) black (48.5) purple (54.5) cinnabar (57.5) vestigial (67.0) Lobe (72.0) and speck (107.0) (MORGAN, BRIDGES and STURTEVANT 1925). If the data given in tables 8 and 9 of the previous paper are restated so as to show the relative proportions of crossover and non-crossover flies, we get the following: TABLE 1 Normal chromosome.