SNP genotyping is the measurement of genetic variations of single nucleotide polymorphisms (SNPs) between members of a species. It is a form of genotyping, which is the measurement of more general genetic variation.
On most plays, the center will snap the ball directly into the quarterback's hands. In a shotgun formation, the center snaps the ball to the quarterback lined up several yards behind him.
Each player/position has a specific role to play. The offensive positions are shown in the lower half of the following figure, and the defensive positions are shown in the upper half. The offense and defense face each other across the line of scrimmage. The line of scrimmage is simply the spot on the field from which the football is hiked.