8. What pteridines are present in brown-eyed flies? 9. Leitenberg and Stokes (19

Question

8. What pteridines are present in brown-eyed flies? 9. Leitenberg and Stokes (1964) found that adult white- and brown-eye mutants possess no pteridines at all! Do your chromatograms support their observations? If not, suggest some possible reasons for the lack of agreement. 10. Eye color in D. melanogaster is the result of the interaction of two groups of pigments, the pteridines and brown ommochromes (Strickberger, 1985). What pteridines are present in scarlet- 11. How do questions 9 and 10 relate to the observed phenotype of the cinnabar, brown double mu- tant flies and the result that this fly stock gave in your chromatogram? 12. On the basis of information in questions 7 through 10, predict the pl flies resulting from a cross between homozygous scarlet-cyed and h enotypes of the F1 and F2 omozygous brown-eyed flies

Explanation / Answer

8. There is no pteridine present in the brown-eyed flies,because they contain the brown pigments called ommochromes. Brown-eye mutation affects one of the enzymes involved in pteridine biosynthetic pathway.

If the chromatogram result does not support this observation,there might be some mutation in the ommochrome synthesis pathway so that the semi-dull effect of brown will be missing and the eye colour will be closer to red i.e presence of some pteridines.

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