Chapter 15: transcription regulation in eukaryotes

A paracrine signaling factor expressed by engrailed cells that activates the Patched receptor on neighboring cells.

A receptor protein on cells neighboring engrailed cells that binds to Hedgehog (Hh), triggering downstream signaling.

A small regulatory RNA molecule that controls gene expression by regulating mRNA stability and translation.

A protein that binds to the target mRNA, blocking its translation into protein. It's crucial for regulating cell lineages in C. elegans.

A technique used to visualize the location of specific mRNA molecules within cells or tissues.

The dorsal lip of the blastopore (also called Spemann's Organizer) is a region in the early amphibian embryo that plays a crucial role in establishing the dorsal axis. When transplanted to the ventral region of a recipient embryo, it induces the formation of a secondary dorsal axis, leading to the development of Siamese twins.

Sonic Hedgehog (Shh) is a signaling protein that plays a vital role in limb development, particularly in establishing the anterior-posterior pattern of digits. When the ZPA, a region at the posterior limb, is transplanted to the anterior limb bud, it induces the formation of extra digits with reversed polarity, a phenomenon attributed to Shh signaling.

Polydactyly is a condition characterized by the presence of extra digits. It can arise from the misexpression of Sonic Hedgehog (Shh) in atypical limb regions, leading to the formation of extra digits. Mutations in cis-acting regulatory elements affecting Shh expression, rather than mutations in the coding region, are responsible for this condition.

Homeotic genes are a class of genes that control the identity of body parts. They specify the developmental fate of different segments or regions of the body. Mutations in these genes can lead to the transformation of one body part into another, as seen in homeotic mutants.

In Drosophila, the Bithorax complex is a group of homeotic genes responsible for controlling the identity of the thoracic and abdominal segments. Mutations in these genes can result in the development of wings on the third thoracic segment, normally the haltere segment, leading to a phenotype known as bithorax.

In Drosophila, the Antennapedia complex is a group of homeotic genes controlling the identity of the head and thoracic segments. Mutations in these genes can result in the development of legs in place of antennae, leading to the Antennapedia mutant phenotype.

Hox genes are a family of homeotic genes that play a crucial role in establishing the body plan in animals. They are characterized by their specific spatial expression patterns and their regulation by other genes. Their order on the chromosome corresponds to their expression domains along the anterior-posterior axis of the body, with genes at the 3' end expressed in more posterior regions.

In situ hybridization is a technique used to detect the localization of specific mRNA molecules in tissues or cells. It utilizes labeled probes, complementary to the target mRNA, to visualize the expression pattern of a particular gene.

Maternal genes are expressed by the mother and deposited into the egg cytoplasm, providing essential factors for early embryonic development. Bicoid, expressed at the anterior pole, establishes a gradient that activates anterior genes, while Nanos, expressed at the posterior pole, creates a gradient for posterior genes.

Gap genes are essential for establishing large segments of the embryonic body plan. They respond to the gradients established by maternal genes, forming broad expression patterns that define specific regions of the embryo. Examples include Kruppel, Knirps, Giant, and Hunchback.