DALLAS — The Lakers took a giant step backward with tonight’s come-from-ahead loss to the Dallas Mavericks. Most of all, their defense was not up to par during a second half meltdown. Dallas went on a 17-2 run near the end of the third quarter to take control. Coach Phil Jackson woofed at Lamar Odom about he importance of team defense and Odom barked back about what only he knows. He didn’t say much after the game, a rare quiet night for the usually chatty sixth man. Pau Gasol had 23 points, topping 13,000 for his career. But he had only six points on 3-for-4 shooting in the second half. The Mavericks shot a season-best 55 percent. Shawn Marion and Jason Terry each had 22 points.