What is the function of the structure identified by the red arrow?

What links the two strands in a dna helix together in the middle? a. phosphate groups b. sugar rings bonded together c. proteins d. bases with hydrogen bonds

Match with o for organic and i for inorganic for each compound

What does polymerase chain reaction (pcr) do? o a. separates dna fragments by size o b. cuts a dna sample into fragments o c. provides an overall picture of a person's chromosomes o d. makes more copies of a sample of dna