Name the enzyme that carries out the transcription of DNA.
Fig. 4.1 shows that the primary transcript is altered by adding nucleotides to both ends of the molecule. The cap shown in Fig. 4.1 is a guanine nucleotide added to the $5'$ end of RNA. The poly(A) tail added to the $3'$ end is made up of many adenine nucleotides. The cap and the tail have a role in stage Y and are also important for the stability and role of mRNA. Suggest the functions of the cap and the poly(A) tail in the stability and role of mRNA.
Describe the process that takes place at stage Y in Fig. 4.1.
The nucleotide sequence TTAGGG is repeated in the direction $5'$ to $3'$ in the telomeres of human chromosomes. State where in a chromosome the telomeres are located.
Outline the role played by telomeres.
Melanoma is a type of tumour that develops from pigment-producing skin cells known as melanocytes. Outline how a tumour may develop from a melanocyte.
A melanoma tumour is cancerous and can spread to other parts of the body. T-vec is a new drug developed to treat melanoma that has spread to other parts of the body, including lymph nodes. T-vec contains a virus that infects some of the melanoma cells, causing the cells to burst and release their contents. Some of the contents of the melanoma cells act as cytokines and others act as antigens. Explain the effects of the cytokines and antigens released from melanoma cells in stimulating the immune system to destroy the cancerous cells.