Nucleic acids and protein synthesis

6.1 Structure and replication of DNA
6.2 Protein synthesis 

Nucleic acids have roles in the storage and retrieval of genetic information and in the use of this
information to synthesise polypeptides. DNA is an extremely stable molecule that cells replicate with
extreme accuracy. The genetic code is used by cells for assembling amino acids in correct sequences to make polypeptides. In eukaryotes this involves the processes of transcription in the nucleus to produce short-lived molecules of messenger RNA followed by translation in the cytoplasm.

Learning Outcomes
Candidates should  be able to:

6.1 Structure and replication of DNA

Understanding the structure of nucleic acids allows an understanding of their role in the storage of genetic information and how that information is used in the synthesis of proteins.

a) describe the structure of nucleotides, including the phosphorylated nucleotide ATP (structural formulae are not required)

b) describe the structure of RNA and DNA and explain the importance of base pairing and the different hydrogen bonding between bases (include reference to adenine and guanine as purines and to cytosine, thymine and uracil as pyrimidines. Structural formulae for bases are not required but the recognition that purines have a double ring structure and pyrimidines have a single ring structure should be included)
c) describe the semi-conservative replication of DNA during interphase

6.2 Protein synthesis 

The genetic code specifies the amino acids that are assembled to make polypeptides. The way that
DNA codes for polypeptides is central to our understanding of how cells and organisms function.

a) state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule

b) state that a gene mutation is a change in the sequence of nucleotides that may result in an altered polypeptide

c) describe the way in which the nucleotide sequence codes for the amino acid sequence in a polypeptide with reference to the nucleotide sequence for HbA (normal) and HbS (sickle cell)
alleles of the gene for the β-globin polypeptide

d) describe how the information in DNA is used during transcription and translation to construct polypeptides, including the role of messenger RNA (mRNA), transfer RNA (tRNA) and the ribosomes