Question

A bidirectional replication initiation site located in the β-globin gene cluster is deleted from the β-globin cluster and transplanted to the ochre gene in a monkey cell, a site at which replication is not normally initiated. The altered cells are grown in culture and their behavior during replication is observed. What happens?

a. Replication is no longer initiated in the β-globin gene cluster, but it is initiated in the ochre gene.
b. Replication is initiated in neither the β-globin gene cluster nor the ochre gene.
c. Replication is initiated in both the β-globin gene cluster and in the ochre gene.
d. Replication is initiated in the β-globin gene cluster, but not in the ochre gene.
e. Replication in the entire cell ceases.

Answer 1

Removing the initiation site from the β-globin gene cluster and inserting it into another gene, such as the ochre gene, would typically result in initiation now occurring at the new location, providing that all necessary factors for replication are present.

Step-by-step explanation:

The alteration of a bidirectional replication initiation site within a gene cluster could affect replication initiation at both the original and the new location. If we consider typical replication behaviors, moving the initiation site from the β-globin gene cluster to another gene (the ochre gene in this case) suggests that replication initiation would follow the movement of the origin.

However, in eukaryotic cells, replication requires more than just the sequence of the origin itself; it requires a proper chromosomal context and associated factors for initiation. Therefore, it is likely that a. Replication is no longer initiated in the β-globin gene cluster, but it is initiated in the ochre gene, assuming that all other necessary replication factors are present at the new location. If these factors or the chromatin context at the ochre gene location do not support replication initiation, it is possible that replication may not initiate there either.