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* FTSE 100 up 0.1%, FTSE 250 adds 0.2%

July 18 (Reuters) - UK's FTSE 100 edged higher at open on Tuesday, led by mining and healthcare stocks, while shares of Ocado jumped after the online supermarket group kept its full-year guidance unchanged.

By 0716 GMT, the blue-chip FTSE 100 added 0.1%, while the more domestically-focussed FTSE 250 midcap index rose 0.2%.

Miners of both industrial and precious metals rose 0.5% each, as most metal prices appreciated on a softer dollar.

Ocado jumped 7.3% after the online supermarket and technology group kept its financial guidance for the year as it reported a return to underlying profit in its first half.

AstraZeneca rose 0.8% after the U.S. Food and Drug Administration (FDA) said it had approved the drugmaker and partner Sanofi's antibody therapy to prevent respiratory syncytial virus (RSV) in infants and toddlers.

Darktrace jumped 20.1% after the cyber-security company said a review by auditing firm EY showed "a number of areas" where its systems, processes or controls could be improved, but added that the report will not impact its previous financial statements. (Reporting by Shashwat Chauhan in Bengaluru; Editing by Varun H K)