Question

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

Short answer

Hox genes are so potent that they serve as "master manage genes." They have the ability to turn a wide variety of genes on or off. Hox genes accomplish this by encoding transcription factors that regulate the expression of a wide range of genes.

Step-by-step solution

1. Hox genes in animals 

Animal structure is determined by genes, or "homeotic genes," which are DNA sequences known as "homeoboxes." Homeobox genes provide transcription factors for proteins. Hox genes are a subset of animal genes that specifically contain homeobox sequences. The general body plan of the animal, including the number of body segments, the number and positioning of appendages, and the animal's directionality from head to tail, is determined by this group of genes.

2. Hox genes in mice

Hox genes are highly conserved genes that encode transcription factors that control how animals develop from the time of conception. The Hox-A, Hox-B, Hox-C, and Hox-D genes are replicated in four clusters on separate chromosomes in vertebrates. These gene clusters' genes are expressed at particular stages of development in specific body parts. The similarity between the hox genes in humans and mice may be seen in the diagram above. Note how the identical body segments in both mice and humans exhibit Hox gene expression, as shown by the orange, pink, blue, and green shading.

3. Control of gene expression by hox genes

By encoding transcription factors that regulate the expression of numerous other genes, hox genes do this. Hox genes are found in all members of the animal kingdom, from worms to flies, mice, and humans. This is because most species share a common origin, making their genetic sequences and locations on chromosomes highly similar. The anteroposterior axis of the animal's body is reflected in gene order. Hox genes have experienced between two and four duplication events during animal evolution, with more genes allowing for the formation of more complex body kinds. This is one factor that has contributed to the increased complexity of the animal body. Hox genes come in four (or more) sets in all vertebrates, although there is only one set in invertebrates.