Which of the following is a characteristic of cancer cells?

• They divide uncontrollably.
• They fail to replicate their DNA.
• They produce antibodies to protect the body.
• They prevent other cells from dividing by mitosis.

Some breast cancers are stimulated to grow by the hormone oestrogen. Explain why removing the ovaries can be an effective treatment for these breast cancers.

Cells usually become cancerous due to damage to their DNA. Scientists have found a gene called BRCA. This gene normally produces a protein that repairs damaged DNA.

In a population of $28000000$ females, 1 in 350 has a mutation in their BRCA gene.

• 70% of women with this mutation could develop breast cancer.
• Calculate how many females in this population could develop breast cancer due to a mutation in the BRCA gene. Show your working.

Genetic testing allows women to discover if they carry the mutated BRCA gene. Carriers may be offered the option of having their ovaries surgically removed before cancer develops. Suggest two reasons why making this choice can be extremely difficult for a woman.