Suppose we wish to construct, using compass and straightedge, angle dae congruent to angle dbc. which step would be correct to do first?

first you need to place a point for the vertex of the new angle. then take the compass and place it on the vertex of angle DBC and draw a circle around it. without adjusting the compass, move it to the vertex that you had placed and draw the same size circle around it. Draw a base line for the new angle . Then  go to the point of intersection on angle DBC where the circle intersects both of the sides. place your compass on both intersection points. move that to the point of intersection on the new angle and draw a circle. then connect the points.

i would need to see the dot plot : )

homozygous. one is homozygous, while two is heterozygous.