DNA mononucleotide - Is this correct?

Can someone check this please:

1. Base bonding: phosphodiester bond via condensation

2. Bonding between adjacent nucleotides: phosphodiester bond, a covalent bond is formed between 5 phosphate group of nucleotide

3. Reactions which form polymers: condensation or hydrolysis?

1. If you're talking about the bonding between base pairs, I'm 99% sure that's hydrogen bonding rather than phosphodiester bonding
2. Yep, that looks right
3. Condensation reactions form polymers, hydrolysis breaks up polymers into monomers (hydro = water, lysis = breaking up)

1. No. Phosphodiester bonds links adjacent sugar molecules (3'➝5') in the sugar-phosphate backbone. Think about how DNA is replicated - if there was strong covalent bonding between base pairs, how would you 'unzip' the DNA molecule to allow replication and transcription? How much energy would be required to break all those covalent bonds? It's hydrogen bonding between bases - and for bonus points look up bonding between pyrimidines and purines. What do you notice about the H bonding?

2. More accuracy needed. See (1) above for how nucleotides are bonded to form the sugar-phosphate backbone. It would help for you to be sure of what a 'phosphodiester bond' is, and what a 'phosphoanhydride' bond is. They're not the same, though you are correct that nucleotides are joined by phosphodiester bonds. Where would you find phosphoanhydride bonds, and why are they important in DNA/RNA synthesis?

3. Condensation - again look at a diagram of two monomers (such as two glucose molecules) next to one another and see if you can find the H₂0 which is 'removed' to form the bond.