Double-stranded DNA breaks arise naturally in meiosis. State the process that is started because of double-stranded breaks during meiosis.
Suggest and explain how mutation 999del5 leads to a very high proportion of breast cancer cases in Iceland compared with the general global population.
Outline the advantages of genetic screening for mutations in BRCA2.
Suggest one advantage to a country of a genetic screening programme for breast cancer that screens for specific mutations in BRCA2 in the population.
Suggest how DNA editing prevented Lcn2 from being expressed in cancer cells.
Suggest why the expression of only Lcn2 was affected.
$\textit{Lipocalin 2 (Lcn2)}$ is a cancer-promoting gene (oncogene). If $\textit{Lcn2}$ is expressed, it can lead to breast cancer. Research is being done to test whether gene editing of $\textit{Lcn2}$ could be used to treat breast cancer. Gene editing was used to treat human cancer cells that had been implanted into mice so that a tumour formed. The treatment stopped $\textit{Lcn2}$ from being expressed in the cancer cells and caused a significant decrease in tumour growth. There was no harmful effect in normal tissues.