B: Nucleic Acids HL

DNA Deoxyribose Nucleic Acid RNA Ribonucleic Acid

• Nucleic acids are polymers made up of monomers known as nucleotides • consist of a 5-carbon (pento) sugar, a nitrogen-containing heterocycle called the base, and a phosphate group • condensation products of a pentose sugar, phosphoric acid and a nitrogenous base

All derivates of either purine (secondary amine) or pyrimidine (tertiary amine) Purine • Adenine (A) • Guanine (G) Pyrimidine • Thymine (T) / Uracil (U) • Cytosine (C)

• A double strand of nucleotides held together by H bonding • Contains thymine • contains 2-deoxyribose • double helix consisting of 2 polynucleotide strands that spiral around an axis • each complete turn is 10 nucleotides in length

• A single strand of nucleotides • contains uracil • contains ribose

• each strand of nucleotides has a repeating sugar-phosphate-sugar-phosphate backbone • base attached to each sugar

• Involves the unwinding and separating of the two strands of DNA by breaking the hydrogen bonds between the base pairs • exposes nucleotides and allows the bases on each of the DNA strands to be used as a template for the formation of a complementary DNA strand • Free nucleotides form complementary base pairs with the DNA template strands

• The sequence of bases in DNA determines the primary structure of proteins synthesized by the cell using a triplet code - the universal genetic code • Chromosomes are long, coiled strands of DNA wrapped around proteins called histones (positively charged –> attracted to negative phosphate groups) • contains genes

• increased nutritional content of crops eg golden rice • increased yield of crops • ability of crops to grow in adverse conditions • improved crop resistance to disease • enhanced taste, texture, quality • improved animal health • improved conservation of water, soil and energy

• not enough knowledge about long term effects • escape of transgenic material into the wild • upset the current balance of ecosystems and food chains • alteration of the composition of a balanced diet • exploitation and monopolisation • ethical considerations