The isolation of a mutation effected Anterio-Posterior patterning of the Drosophila embryos are
a. If in a mutation, every other segment of the developing larva is missing, we will consider this mutation to be a mutation in a pair-rule gene. The function of pair-rule gene is the development of segmented embryo and they act at double segment periodicity. So absence of pair-rule gene function results in alteration in the normal developmental pattern in alternate segments.
b. Every region which has the expression of certain gene can be mapped to specific coordinates along Anterio-Posterior and dorsoventral axis. In a repeated pattern of seven stripes along AP axis of the developing embryo, we have to search for the expression of the messenger Ribonucleic acid (mRNA) from the candidate gene. The pair-rule genes act at a double-segment periodicity. Different parts of each double segment are missing in pair-rule mutants. We see the expression of pair-rule genes in striking stripes. Every two segments have one transverse stripe. So in a total of 7 stripes there are 14 future body segments.