nucleic acids A1.2

dna

dna

• genetic material of all living organisms

• double helix

• made of nucleotides

dna nitrogenous bases

adenine, thymine, guanine, cytosine

nucleotide structure

phosphate, sugar, base

nucleotide

single unit of nucleic acid

difference in rna and dna sugar

one less oxygen in dna sugar (on second carbon)

how is a strand of nucleotides joined

• covalent bonds between phosphate and sugar (phosphodiester bond)

• sugar-phosphate backbone

condensation reactions

• anabolic - join monomers to make polymers

• endothermic - require energy to take place

• creates covalent bond

• water is produced as byproduct

which bases are purines

adenine and guanine - larger bases with additional ring

which base are pyramindines

thymine, uracil, cytosine - single ring

complementary base pairing

• each base will only line up properly with one other (a-t and g-c)

• hydrogen bonds hold them together (2 for at and 3 for gc)

nucleosomes

regions of dna wrapped around 8 proteins called histones with an additional one to lock it into place

euchromatin

• loosely bound nucleosomes to each other

• can be transcribed

heterochromatin

tightly bound