Question

Which of these statements about vertebrate limb formation are correct?

A. Cells from the ZPA and AER migrate throughout the limb bud and turn on Hox genes of other cells that they encounter.
B. Hox genes that originally evolved in the context of specifying the anterior-posterior body axis have been co-opted to coordinate the growth of complex limbs.
C. Hox gene expression remains the same until the stylopod, zeugopod, and autopod are all fully developed.
D. The Sonic hedgehog genes, the FGF-4 and 8 genes, and the Wnt7a gene establish the axes of the limb. These genes are not part of the Hox gene family, but they influence Hox gene expression.
E. A cell in a vertebrate limb bud "knows" where it is through the relative concentration it experiences of certain proteins that, in turn, are only secreted from certain cells in certain areas of the limb bud.

Answer 1

The correct statements regarding vertebrate limb formation are that Hox genes have been co-opted to govern limb growth, Sonic hedgehog and other genes influence Hox gene expression in limb axes establishment, and cells in the limb bud determine their position by signal concentration.

Step-by-step explanation:

The vertebrate limb formation involves complex genetic regulations and signaling. In the context of the correct statements presented:

• B. Hox genes that originally evolved in the context of specifying the anterior-posterior body axis have been co-opted to coordinate the growth of complex limbs. This is seen in both mouse and human embryos where Hox gene expression aligns with specific body segments.
• D. The Sonic hedgehog genes, the FGF-4 and 8 genes, and the Wnt7a gene establish the axes of the limb. These genes are not part of the Hox gene family, but they influence Hox gene expression.
• E. A cell in a vertebrate limb bud "knows" where it is through the relative concentration it experiences of certain proteins that, in turn, are only secreted from certain cells in certain areas of the limb bud.

These concepts highlight the intricate processes guiding the development of vertebrate limbs, where Hox genes and other molecular signals work in coordination to establish the correct structure and orientation of the limbs.