AP BIOLOGY

Detailed explanation-1: -DNA is always synthesized in the 5’-to-3’ direction, meaning that nucleotides are added only to the 3’ end of the growing strand. As shown in Figure 2, the 5’-phosphate group of the new nucleotide binds to the 3’-OH group of the last nucleotide of the growing strand.

Detailed explanation-2: -DNA replication goes in the 5’ to 3’ direction because DNA polymerase acts on the 3’-OH of the existing strand for adding free nucleotides.

Detailed explanation-3: -New DNA is made by enzymes called DNA polymerases, which require a template and a primer (starter) and synthesize DNA in the 5’ to 3’ direction. During DNA replication, one new strand (the leading strand) is made as a continuous piece.

Detailed explanation-4: -When we look at a sequence of DNA, we read it in the 5′-3′ direction. The relative positions of genes or other sites along a DNA strand can be described as upstream (towards the 5′ end) or downstream (towards the 3′ end).

Detailed explanation-5: -Leading Strand and Lagging Strand The first one is called the leading strand. This is the parent strand of DNA which runs in the 3’ to 5’ direction toward the fork, and it’s replicated continuously by DNA polymerase because DNA polymerase builds a strand that runs antiparallel to it in the 5’ to 3’ direction.