A hypothetical cell lineage is shown here.

A gene, which we will call gene X, is activated in the B-l cell, so the B-l cell will progress through the proper developmental stages to produce three nerve cells (D-l, D-2, and D-3) and one muscle cell (D-4). Gene X is normally inactivated in A-l, C-l, and C-2 cells, as well as the four D cells. Draw the expected cell lineages if a heterochronic mutation had the following effects:
A. Gene X is turned on one cell division too early.
B. Gene X is turned on one cell division too late.

A-1 B-1 C-1 Nerve cellMuscle cell Epidermai cell