Early development depends on the temporal and spatial interplay between maternally supplied material and mRNA and the onset of zygotic gene expression. Maternally encoded mRNAs must be produced, positioned, and degraded [Surdej and Jacobs-Lorena (1998). Mol. Cell Biol. 18:2892–2900]. For example, transcription of the bicoid gene that determines anterior– posterior polarity in Drosophila is maternal. The mRNA is synthesized in the ovary by nurse cells and then transported to the oocyte, where it localizes to the anterior ends of oocytes. After egg deposition, bicoid mRNA is translated and unstable bicoid protein forms a decreasing concentration gradient from the anterior end of the embryo. At the start of gastrulation, bicoid mRNA has been degraded. Consider two models to explain the degradation of bicoid mRNA: (1) degradation may result from signals within the mRNA (intrinsic model), or (2) degradation may result from the mRNA’s position within the egg (extrinsic model). Experimentally, how could one distinguish between these two models?
Early development depends on the temporal and spatial interplay
between maternally supplied material and mRNA and
the onset of zygotic gene expression. Maternally encoded
mRNAs must be produced, positioned, and degraded [Surdej
and Jacobs-Lorena (1998). Mol. Cell Biol. 18:2892–2900].
For example, transcription of the bicoid gene that determines
anterior–
posterior polarity in Drosophila is maternal. The
mRNA is synthesized in the ovary by nurse cells and then transported
to the oocyte, where it localizes to the anterior ends of
oocytes. After egg deposition, bicoid mRNA is translated and
unstable bicoid protein forms a decreasing concentration gradient
from the anterior end of the embryo. At the start of gastrulation,
bicoid mRNA has been degraded. Consider two models to
explain the degradation of bicoid mRNA: (1) degradation may
result from signals within the mRNA (intrinsic model), or (2) degradation may result from the mRNA’s position within the
egg (extrinsic model). Experimentally, how could one distinguish
between these two models?
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