Introduction to Genetic Analysis 596

Introduction to Genetic Analysis 596 - that the...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: that the transcription factors encoded by the gap genes regulate two different sets of target genes. First, let’s briefly consider the formation of segment number. (Refer to Figure 18-22 for a description of the mutant phenotypes produced by the different classes of segment-number genes.) The gap genes activate a set of A–P patterning genes called the pair-rule genes, each of which encodes a transcription factor, expressed in a re- peating pattern of seven stripes (see Figure 18-23b). The different pair-rule genes produce a slightly offset pattern of stripes, as shown by the gray and reddish bands in Fig- ure 18-23b. Within a given cell, several different pair- rule proteins are expressed. There is a hierarchy within the pair-rule-gene class. Some of them, called primary pair-rule genes, are regulated directly by the gap genes. How do the asymmetrically dis- tributed gap genes produce the repeating seven stripe ex- pression pattern of the primary pair-rule genes? The gap proteins at work here are expressed in a very different, asymmetrical pattern. The key is that the regulatory ele- ments for certain pair-rule genes are quite complex. One primary pair-rule gene is eve (even-skipped). The eve gene contains separate enhancer elements, each of which inter- acts with different combinations of gap transcription fac- tors to produce the seven eve stripes. For example, the en-stripes....
View Full Document

This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

Ask a homework question - tutors are online