Biol168_10F_Lecture 6_6Oct2010

Biol168_10F_Lecture 6_6Oct2010 - Dr. Morris Maduro, UC...

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Dr. Morris Maduro, UC Riverside Biology 168 – 10F – Lecture 6, page 1 Lecture #6: Drosophila : Pair-Rule Genes Text: 2nd Ed.: 170-174. 3rd Ed.: 61-65. Some figures in these notes are redrawn from Wolpert et al. (2nd edition). The Pair-Rule Genes Segments and Parasegments The fundamental units of segmentation in the embryo are called parasegments . These represent domains of gene expression that will ultimately generate the segments seen in the adult. There are 14 parasegments, and the final segments (C1-C3, the head segments, which ultimately fuse together; T1-T3, the thoracic segments; and A1-A8, the abdominal segments) are offset anteriorly from the parasegments by approximately half a segment: anterior posterior The pair-rule genes (8 are known) are so named because loss of function results in a phenotype in which every other segment is deleted from the embryo. This class of phenotype was somewhat unexpected to Nüsslein-Volhard and Wieschaus, because the other classes of mutations affected either large contiguous regions of the embryo, or individual segments; there is no reason to propose the specification of segments in pairs. Two examples are the genes
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Biol168_10F_Lecture 6_6Oct2010 - Dr. Morris Maduro, UC...

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