Chapter 27, Problem 1VCQ

Figure 27.5 If a Hox 13 gene in a mouse was replaced with a Hox 1 gene, how might this alter animal development?

Summary Introduction

To analyze:

The development of the mouse if the Hox13 gene is replaced by the Hox1 gene.

Introduction:

Homeotic genes are the regulatory genes that control the development of body structures. One such set of genes called the Hox genes are the group of the related genes that control the body plan of an embryo along the head-tail axis.

Explanation of Solution

Among the vertebrates, humans and mice show the duplication of the Hox genes over the period of evolution. They are present in the four gene clusters on four different chromosomes called Hox- A, Hox- B, Hox- C and Hox- D. The genes within these clusters express in certain body segments at a particular stage of development.

The genes show homology in humans and mice and the genes Hox 1-4 are involved in the development of the head and the genes Hox 9-13 are involved in the development of the limbs in humans and the tail in the mouse. If a Hox- 13 gene is replaced by a Hox- 1 gene in the mouse, it might develop two heads due to the presence of two Hox-1 genes and lack a tail due to the missing Hox- 13 gene.

Conclusion

Thus, the replacement of Hox- 13 genes by Hox- 1 gene in the mouse can lead to the formation of a mouse with two heads and no tail.