Why are hox genes found in different animals very similar to each other?

Answer 1

Hox genes in different animals are very similar to each other because they have very important functions during development: they tell each region of the embryo what kind of body segment to turn into. Think about what would happen to you if this process went wrong: your body parts wouldn't be in the right places, or you might be missing body parts altogether! It's therefore very important to keep these genes in working order, and that means not changing them too much.

But how can essentially the same Hox gene be responsible for making head parts in a fly and head parts in a human, since our head parts don't look much alike? The answer is that Hox genes like to boss around other genes, and who they boss around can change. Hox genes tell a region of an embryo what to become by switching on certain subsets of genes and switching off other subsets. For example, in fruit flies, the Hox gene called Scr activates the subset of genes that turns cells into salivary glands. Also in fruit flies, the Hox gene Ubx turns off genes that activate wing development (so that wings do not develop). If these Hox genes are mutated to the point that they can no longer function, then the fly would have no salivary glands, and would have wings where it shouldn't! However, humans don't have wings, and our salivary glands are different from those of flies. Although we use essentially the same Hox genes, they've evolved to switch on or off different genes. In other words, the Hox Head Honcho is the same, but the employees are different.

Answer 2

Hox genes in different animals are very similar to each other because they have very important functions during development: they tell each region of the embryo what kind of body segment to turn into. Think about what would happen to you if this process went wrong: your body parts wouldn't be in the right places, or you might be missing body parts altogether! It's therefore very important to keep these genes in working order, and that means not changing them too much. But how can essentially the same Hox gene be responsible for making head parts in a fly and head parts in a human, since our head parts don't look much alike? The answer is that Hox genes like to boss around other genes, and who they boss around can change. Hox genes tell a region of an embryo what to become by switching on certain subsets of genes and switching off other subsets. For example, in fruit flies, the Hox gene called Scr activates the subset of genes that turns cells into salivary glands. Also in fruit flies, the Hox gene Ubx turns off genes that activate wing development (so that wings do not develop). If these Hox genes are mutated to the point that they can no longer function, then the fly would have no salivary glands, and would have wings where it shouldn't! However, humans don't have wings, and our salivary glands are different from those of flies. Although we use essentially the same Hox genes, they've evolved to switch on or off different genes. In other words, the Hox Head Honcho is the same, but the employees are different.

Answer 3

That these many types of organisms stem from common ancestry.

Answer 4

No, that is not true.