The pictures shown are those of the "dinning room" [phosphate + sugar} and the "bucket truck" [nucleotide base]. Remember, you are standing on the five sided dinning room table which is the five sided sugar. The bucket truck is attached to the 1st dinning room chair (carbon one). To extend the bucket out the window is to place the nucleotide base into the world of the helix that is seeking its partner. It is a change in a single bucket that defines the SNPs (snips).