You are a professor running a lab investigating insect developmental genetics. Y

Question

You are a professor running a lab investigating insect developmental genetics. Your graduate student bursts into your office with photographs of a mutant pigmentation phenotype she has just discovered. The mutation shifts pigment stripes on each abdominal segment from the anterior to posterior portion of each segment. The mutation appears to be controlled by a mutation in a single gene (it exhibits Mendelian inheritance). Your student thinks this phenotype represents a Homeotic mutation and must be controlled by a member of the Hox protein family.

3b. The good news is that you are confident that this mutation has occurred in another class of genes operating in the developmental tool kit. In particular, you note that all of the body segments are present in the mutant. Additionally, you note that this mutation affects the orientation of the phenotype within each segment.

What is the most likely class of tool kit gene mutation to cause this phenotype? Explain why the lack of any missing body segments in the mutant insect allows you to rule out mutations in any other class of toolkit gene.

Explanation / Answer

Here only maternal effect genes are responsible for such cases. Hox genes do not express in whole body of drosophila. Each hox gene has its distinct boundary or segment. Caudal and hunchback like maternal effect genes express throughout the body and regulated by the level of their own class proteins. For example, hunchback expression regulates by nanos and pumilio protein. Therefore, mutation in maternal effect genes may deregulate the expression of bicoid, nanos, hunchback, and caudal genes, in their respective zones.

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