A-Level Biology Specification

OCR B H422

Section 2.1.4: Nucleic acids

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#2.1.4a

the structure of a nucleotide as the monomer from which nucleic acids are made

To include the differences between RNA and DNA nucleotides, the identification of the purines and pyrimidines, the type of pentose sugar and the formation of phosphodiester bonds (the sugar phosphate ‘backbone’).

#2.1.4b

the structure of adenosine di-phosphate (ADP) and adenosine tri-phosphate (ATP) as phosphorylated nucleotides

#2.1.4c

(i) the structure of the DNA molecule, including a review of the evidence for complementary base pairing (Chargaff’s rules)

(ii) practical investigation into the purification of DNA by precipitation

#2.1.4d

semi-conservative DNA replication

To include the roles of the enzymes helicase and DNA polymerase, the importance of replication in conserving genetic information with accuracy and the occurrence of random, spontaneous mutations.

#2.1.4e

the nature of the genetic code

To include reference to the triplet, non-overlapping, degenerate and universal nature of the code and how a gene determines the structure of proteins including enzymes by ordering the sequence of amino acids in a polypeptide.

#2.1.4f

the structure of RNA (ribonucleic acid) and how it differs from that of DNA

#2.1.4g

transcription and translation of genes resulting in the synthesis of polypeptides

To include the role of RNA polymerase, messenger (m)RNA, transfer (t)RNA and ribosomal (r)RNA (details of post transcriptional modification are not required).