Why? What is the specific question or hypothesis being tested for this figure? H

Question

Why? What is the specific question or hypothesis being tested for this figure?

How? Methods: Describe how the experiment was performed.

What? Results. Summarize the experimental results, highlighting the relevant controls and main conclusions that can be made only from the data in this figure.

So what? Conclusions. Summarize the conclusions from this figure (and only this figure!)

opossum st. 27 mouse E9.5 st. 27 Hoxc6 opossum mouse 9 Hoxc6 st. 27 E9.5 G Hoxbs H Hoxc6: Fig. 10. Hox expression in opossum and mouse correlates with the forelimb heterotopy. (A,B) Eight somites are medial to the opossum forelimb (A) and six in mouse (B). The dashed line outlines the Lateral views, with anterior to the top left. (C-F) Hoxb5 (C,D) and Haxc6 views, anterior is to the left. (G,H) Schematic contrasting opossum and mouse Hoxb5 (G) and Hoxc6 (H) expression in the somites and lateral in the lateral plate mesoderm of opossum relative to mouse, as well as the posterior shift in Hoxc6 expression in the somites of opossum relative to mouse. Vertical dashed lines indicate the anterior (left) and

Explanation / Answer

Hox genes code for homeodomain-containing transcription factors that pattern the rostral–caudal (R/C) axis during embryogenesis.

Their differential expression pattern along the R/C axis is tightly regulated in both neural and nonneural tissue, and it is the product of diverse, and sometimes opposing, regulatory influences.

Important developmental signaling pathways, such as the retinoic acid and fibroblast growth factor pathways, along with developmentally regulated transcription factors initiate their expression, which is subsequently maintained and refined by their own gene products through auto- and cross-regulatory mechanisms.

Posttranscriptional mechanisms further refine these patterns and boundaries, resulting in a pattern of Hox gene expression that is unique at different levels of the embryonic R/C axis and participates in their specification.

Organisation of Hox clusters in mouse.

Hox genes (top) are grouped into two genomic clusters: the Antennapedia (ANT-C) and Bithorax clusters (BX-C).

Expression domains of the individual Hox genes within the ANT-C and BX-C along the anteroposterior (AP) axis of the fruitfly embryo match the array of the genes along the chromosome, displaying a property termed collinearity.

An important difference between these two systems is that the mouse has four clusters (Hoxa, Hoxb, Hoxc and Hoxd) instead of one, as a result of two rounds of gene duplication.

The Hox complement of the mouse also reveals that some individual Hox genes have been duplicated whereas others have been lost in each cluster.

Based on sequence and genomic comparisons across a wide range of phyla, the structure of the cluster ancestral to insects and mammals can be inferred.

Several microRNAs (miRNAs) are also encoded within the mouse Hox clusters, and many of these miRNAs have been shown to target Hox genes.

Furthermore, the relative position of many of these miRNA genes in reference to nearby Hox genes appears to be invariant despite substantial periods of evolution, suggesting that the position of miRNA genes might be functionally constrained.  

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.