Final answer:
Option 1 is correct option. Hox genes are crucial in laying out the basic body form during the development of many animals, including humans, flies, and worms.
Step-by-step explanation:
The Role of Hox Genes in Animal Development
Hox genes are part of an ancient genetic toolkit that plays a crucial role in the development of many animals, including humans, flies, and worms. During embryonic development, these genes are responsible for laying out the basic body form such as the number of segments, the placement of limbs, and head-tail directionality. These genes contain DNA sequences called homeoboxes, which encode protein transcription factors that control the expression of numerous other genes, effectively acting as master control genes.
In the situation of the fruit fly, Drosophila melanogaster, a single Hox mutation can result in dramatic alterations such as an extra pair of wings or legs where antennae should be. This demonstrates the power of Hox genes in determining anatomical structures and their locations. The homology of these genes among various species suggests a common ancestor, and variations in these genes contribute to the diversity of body plans within the animal kingdom.
Multiple clusters of Hox genes are present in vertebrates, and these clusters are expressed in corresponding body segments in mammals like mice and humans. Such complexity in vertebrates may be partly attributed to the duplication events in their evolutionary history. These duplicated Hox genes have allowed for more intricate body plans to evolve, which is a crucial factor in the complexity of vertebrate development.
In answering the student's question, it is option 1) The lay out the basic body form of many animals (humans, flies, and worms) that Hox genes are responsible for during development. This includes determining the number and placement of body segments and appendages, as well as establishing the directional axis of the body plan from head to tail.