The 49ers officially signed defensive end Jaylon Allen to a one-year deal today, placing DL Tarron Jackson on injured reserve following his neck injury.

San Francisco placed defensive lineman Tarron Jackson on the Injured Reserve List, two days after he suffered a neck injury in a team practice. In a corresponding transaction, the team signed defensive lineman Jaylon Allen, most recently of the United Football League’s Memphis Showboats, to a one-year contract.

Two days after a scary incident in which he was taken off the field on a stretcher, San Francisco 49ers defensive end Tarron Jackson has landed on injured reserve. The Niners announced Tuesday that they've placed Jackson on IR with what the team is calling a neck injury he suffered midway through Sunday's practice.