Complex sentence: Tucker has worked for the Houston Museum of Fine Arts since 1976, when it possessed virtually no photographs, becoming its curator of photography in 1978 and having a major responsibility for increasing its holdings of photographs to over 24,000 in 2008.
Split into simpler sentences: Tucker has worked for the Houston Museum of Fine Arts since 1976, when it possessed virtually no photographs. She became curator of photography in 1978, and has increased the museum's holdings of photographs to over 24,000 in 2008.