IB Chemistry HL Option B Biochemistry B.8 Nucleic acids

IB Chemistry HL Option B Biochemistry B.8 Nucleic acids

• Nucleotides are the condensation products of a pentose sugar, phosphoric acid and a nitrogenous base—adenine (A), guanine (G), cytosine (C), thymine (T) or uracil (U).
• Polynucleotides form by condensation reactions.
• DNA is a double helix of two polynucleotide strands held together by hydrogen bonds.
• RNA is usually a single polynucleotide chain that contains uracil in place of thymine, and a sugar ribose in place of deoxyribose.
• The sequence of bases in DNA determines the primary structure of proteins synthesized by the cell using a triplet code, known as the genetic code, which is universal.
• Genetically modified organisms have genetic material that has been altered by genetic engineering techniques, involving transferring DNA between species.
• Explanation of the stability of DNA in terms of the interactions between its hydrophilic and hydrophobic components.
• Explanation of the origin of the negative charge on DNA and its association with basic proteins (histones) in chromosomes.
• Deduction of the nucleotide sequence in a complementary strand of DNA or a molecule of RNA from a given polynucleotide sequence.
• Explanation of how the complementary pairing between bases enables DNA to replicate itself exactly.
• Discussion of the benefits and concerns of using genetically modified foods.
(Structures of the nitrogenous bases and ribose and deoxyribose sugars are
given in the data booklet in section 34. Knowledge of the different forms of RNA is not required. Details of the process of DNA replication are not required. Limit expression of DNA to the concept of a four-unit base code determining a twenty-unit amino acid sequence. Details of transcription and translation are not required.)