State the structural features in DNA that contribute to its stability.
DNA has been described as a ‘carrier of coded information’. Explain what is meant by this statement.
State at what point in the cell cycle DNA replication takes place.
Two alleles of the gene for the $\beta$-haemoglobin polypeptide exist: HbA (normal) and HbS (sickle cell). Describe and explain how the HbA and HbS alleles of this gene differ.
DNA polymerase is an enzyme needed for DNA replication. One substrate required by DNA polymerase is ATP. ara-ATP is a chemical that changes DNA polymerase activity. In an investigation, the effect of different concentrations of ATP on the rate of DNA synthesis was measured: with no ara-ATP, with a low concentration of ara-ATP, and with a high concentration of ara-ATP. The findings are shown in Fig. 5.1. Explain, in terms of enzyme mode of action, the results shown in Fig. 5.1.