Complete the following passage describing the genetic and cellular mechanisms that control tissue remodeling and development, using the most appropriate biological terms.

The development of a body plan is regulated by genetic factors as well as (1) ............................................ influences. Both internal and external (2) ............................................ trigger signaling cascades that alter the expression of genes governing cell division and cell death. The highly coordinated process of programmed cell death, known as (3) ............................................ , is essential for morphogenetic changes such as the removal of interdigital webbing. During this process, active intracellular (4) ............................................ break down the internal components of the cell. The resulting apoptotic bodies are subsequently engulfed and cleared through (5) ............................................ to protect surrounding tissues from inflammatory damage. [5]

Identify the specific group of regulatory genes, characterized by a highly conserved 180-base-pair DNA sequence, that determine the identity and positioning of anatomical segments along the head-to-tail axis of animal embryos. [1]