Maternal Effect Genes in Embryonic Development

The three main classes of maternal effect genes are: 1) Anterior specification (e.g. Bicoid), 2) Posterior specification (e.g. Nanos), and 3) Both ends specification (e.g. Torso).

Maternal mRNAs such as Torso mRNA are laid down by the mother in a graded fashion, and these mRNAs specify the terminal regions of the embryo.

The Torso protein is a receptor tyrosine kinase that is ubiquitously expressed but only activated at the termini of the embryo, via its activator Torso-Like. Torso-Like protein controls the local secretion of Trunk, which acts as the ligand for Torso.

<p>Bicoid and Nanos mRNAs are deposited at opposite ends of the embryo. They encode transcription factors that act via a gradient mechanism to set up the anterior-posterior axis, with Bicoid specifying the anterior and Nanos specifying the posterior.</p> Signup and view all the answers

<p>The combinatorial effect of different levels of Bicoid, Nanos, Caudal (maternal effect), and Hunchback (maternal effect and zygotic gap gene) along the length of the embryo dictates the expression domains of target genes (gap genes).</p> Signup and view all the answers

<p>Bicoid mutants result in embryos with no head region, while Nanos mutants result in embryos with no tail region.</p> Signup and view all the answers

<p>It is a receptor tyrosine kinase that is activated at the terminal ends of the embryo.</p> Signup and view all the answers

<p>They form opposing concentration gradients that specify the anterior and posterior regions of the embryo.</p> Signup and view all the answers

<p>It is involved in the repression of the Hunchback gene by Nanos.</p> Signup and view all the answers

<p>They lack the head region and have no anterior structures.</p> Signup and view all the answers

<p>It controls the local activation of the Torso receptor tyrosine kinase at the terminal ends of the embryo.</p> Signup and view all the answers

<p>They regulate the translation of target mRNAs by acting as either transcriptional repressors or activators.</p> Signup and view all the answers