Master genes that affect development tend to be highly ; therefore, similarities in patterns of embryonic development reflect shared ancestry that can be evolutionarily ancient.

Master genes tend to be conserved.

Explanation:

Master genes, which are the genes in the DNA that control major development processes such as the development of the skeleton, the organs etc and the production of the necessary proteins.

Since they take on such an important role, they don't really change much. Master genes that affect development tend to be highly conserved so embryonic development can show similar patterns.

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