1.1. DNA mutations can occur at any point during DNA replication but are usually removed by processes in the nucleus. Sometimes these mutations can go undetected. Describe what a base substitution is and explain its possible effects.

1.2. Meiosis and mitosis share some similarities and differences within their cycles. Complete Table 1 below by inserting an X in the appropriate boxes. 

Table 1

1.3. Spider mites are small invertebrate organisms that are found on the island of Mauritius.It has very few chromosomes, 2n = 4. Figure 1 shows some cells that are undergoing cell division.

Figure 1 

Which of these cells belong to the spider mite. Explain your answer. 

1.4. A sample of cells was taken from the spider mites reproductive organs and the mass of DNA was determined. Some of the cells’ DNA had a mass of 3.4 arbitrary units (au) whilst for other cells, it was 6.8. Use your knowledge of the cell cycle to explain this observation.