While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Sequenom (NASDAQ:SQNM) gained about 2% today after Jefferies resumed coverage on the genetic analysis specialist with a buy rating.

So what: Along with the upgrade, analyst Brandon Couillard boosted his price target to $5.00 (from $4.50), representing about 26% worth of upside to yesterday's close. So while contrarian traders might be turned off by Sequenom's year-to-date price strength, Couillard's call could reflect a sense on Wall Street that its growth prospects still aren't fully baked into the valuation.

Now what: Jefferies lifted its 2014 EPS outlook for Sequenom from ($0.75) to ($0.31). "Our revised revenue and EPS forecasts reflect the effects of SQNM's recent divestiture of its Biosciences unit, as well as expectations for a profitability & cash flow inflection in 4Q14," said Couillard. Given Jefferies' solid stock-picking track record -- currently ranked in the top 15% of our CAPS community -- biotech-savvy Fools might want to take a closer look at Sequenom.