TIMELINE-Roche and Genentech

Feb 24 (Reuters) - Genentech DNA.N has urged shareholders to reject Roche's (ROG.VX) $42 billion offer to buy the portion of the U.S. biotechnology company it does not already own.

The Swiss drugmaker will likely have to up its bid, analysts said on Tuesday.[ID:nLO369268]

Following are key developments in Roche's relationship with Genentech.

APRIL, 1976

Genentech -- considered the founder of the biotechnology drugs industry, based on developing genetically modified copies of naturally occurring human proteins -- founded by venture capitalist Robert Swanson and biochemist Herbert Boyer.

FEBRUARY, 1990

Genentech agrees to sell a controlling stake to Roche for $2.1 billion. Under the terms of the deal, Roche would own about 60 percent of Genentech's voting stock.

JUNE, 1999

Roche exercises a call option to buy the portion of Genentech it does not own, then reissues up to 19 percent of the stock, preserving the biotech's status as an independently traded company. Roche later makes a further offerings of Genentech shares.

JULY, 2008

Roche offers to acquire all outstanding shares in its U.S. partner Genentech for $43.7 billion in cash to reinforce its position in cancer medicines.

AUGUST, 2008

Genentech rejects Roche's offer to acquire the outstanding 44 percent, but says it would be willing to consider a sweetened bid.

SEPTEMBER, 2008

Genentech shares slide below the offer price from Roche as spreading market turmoil stokes uncertainty about the takeover and the scope for an improved bid.

JANUARY, 2009

Roche turns hostile, cutting the value of its bid to $42 billion, or $86.50 per share in cash. The offer is at a premium of nearly 3 percent to Genentech's closing price the previous day.

FEBRUARY, 2009

A special committee of Genentech's board recommends shareholders reject Roche's bid, saying it substantially undervalues the U.S. company.

(Reporting by Sam Cage in Zurich; editing by John Stonestreet)