In Drosopbila, recessive mutations in the dorsal-ventral...

Name: Problem 8, Chapter 20: Principles of Genetics
Uploaded: 2020-06-24T07:52:23-08:00
Duration: 22 s
Channel: Sam Limsuwannarot
Description: In Drosopbila, recessive mutations in the dorsal-ventral axis gene dorsal (dl) cause a dorsalized phenotype in embryos produced by dl/dl mothers; that is, no ventral structures develop. Predict the phenotype of embryos produced by females homozygous for a recessive mutation in the anterior-posterior axis gene nanos.

In Drosopbila, recessive mutations in the dorsal-ventral axis gene dorsal (dl) cause a dorsalized phenotype in embryos produced by dl/dl mothers; that is, no ventral structures develop. Predict the phenotype of embryos produced by females homozygous for a recessive mutation in the anterior-posterior axis gene nanos.

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Key Concepts

Maternal Effect Genes

Maternal effect genes are those whose products (RNA or protein) are deposited into the egg by the mother and are critical for early embryonic development. Their function is crucial because the embryo relies on these maternally contributed factors before its own genome becomes active. Mutations in these genes, even if only in the mother, can lead to severe developmental defects in the offspring.

Anterior-Posterior Axis Formation

The anterior-posterior (head-to-tail) axis is one of the fundamental body axes in embryonic development. It is established through a series of molecular gradients and signaling events that specify distinct regions along the length of the embryo. Proper formation of the anterior and posterior structures is essential for the correct spatial organization of the body plan.

Nanos Gene Function

The nanos gene, a well-known maternal effect gene, plays a crucial role in posterior patterning in Drosophila. It helps to establish a gradient that is necessary for the formation of posterior structures such as the abdomen. In mutants lacking functional nanos, embryos typically fail to develop proper posterior segments, leading to an anteriorized phenotype where posterior identity is lost or greatly reduced.

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