<｜begin▁of▁sentence｜>### Instruction:
As a gene therapist working on developing and implementing gene therapy treatments and interventions for genetic disorders and diseases, you may use the NetworkX library in Python to represent genetic networks. For example, when creating a network to model gene interactions, you can add five genes as vertices and then use the `vcount` function to determine the number of vertices in the graph.
### Response:
import igraph as ig
# Create an empty graph
g = ig.Graph()
# Add 5 vertices to the graph
g.add_vertices(5)
# Count the number of vertices in the graph
num_vertices = g.vcount()
print('Number of vertices:', num_vertices)
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