Gunter Korge examined several proteins that are secreted from the salivary glands of Drosophila melanogaster during larval development (G. Korge. 1975. Proceedings of the National Academy of Sciences of the United States of America 72:4550–4554). One protein, called protein fraction 4, was encoded by a gene found by deletion mapping to be located on the X chromosome at position 3C. Korge observed that, about 5 hours before the first synthesis of protein fraction 4, an expanded and puffed-out region formed on the X chromosome at position 3C. This chromosome puff disappeared before the end of the third larval instar stage, when the synthesis of protein fraction 4 ceased. He observed that there was no puff at position 3C in a special strain of flies that lacked secretion of protein fraction 4. Explain these results. What is the chromosome puff at region 3, and why does its appearance and disappearance roughly coincide with the secretion of protein fraction 4?
Gunter Korge examined several proteins that are secreted from the
salivary glands of Drosophila melanogaster during larval development
(G. Korge. 1975. Proceedings of the National Academy of Sciences of
the United States of America 72:4550–4554). One protein, called protein
fraction 4, was encoded by a gene found by deletion mapping to be
located on the X chromosome at position 3C. Korge observed that, about
5 hours before the first synthesis of protein fraction 4, an expanded and
puffed-out region formed on the X chromosome at position 3C. This
chromosome puff disappeared before the end of the third larval instar
stage, when the synthesis of protein fraction 4 ceased. He observed that
there was no puff at position 3C in a special strain of flies that lacked
secretion of protein fraction 4. Explain these results. What is the
chromosome puff at region 3, and why does its appearance and
disappearance roughly coincide with the secretion of protein fraction 4?
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