def check_coverage_threshold(pol, min_cov):
    """Check if coverage for each position is above threshold.
    Returns percentage of bases that pass the coverage threshold"""
    column = str(min_cov) + "X_Coverage"
    pol.loc[pol["total_bases"] >= min_cov, column] = "Yes"
    pol.loc[pol["total_bases"] < min_cov, column] = "No"
    if "Yes" in pol[column].values:
        pct_coverage = pol[column].value_counts()["Yes"] / len(pol) * 100
    else:
        pct_coverage = 0
    return pct_coverage