Question

Consider the following mouse knockout. Why do you think the knockout mouse is much smaller? (2 points) +/+ -/- Brca1 Brca1 mut wt

Answer 1

The brca1 gene is the one which is responsible for production tumor suppressor protein and it helps in preventing the cells from rapidly growing and dividing and hence prevents its uncontrolled growth. Hence, BRCA1 proteins also helps in repairing the DNA that is damaged. The reason why in the knocked out mice the size is smaller is because the Brca1 gene is not expressed, it is not able to produce the tumor suppressor proteins and hence the genetic material that is damaged cannot be repaired. Since it is knocked off, it is not expressed and hence DNA cannot be repaired, and neither can it destroy the cell for which the DNA has been destroyed. This leads to damage in the cells and hence it leads to smaller size of the mice. The brca1 gene is knocked off and hence the embryo tend to show defect due to uncontrolled proliferation and hence makes it more susceptible to retarded growth.