Cancer is caused by changes in cells - OCR Gateway - GCSE Biology - Question 19 - 2021 - Paper 1

To calculate how many females in the UK could develop breast cancer due to a mutation in the BRCA gene:

1. Calculate the number of females with a mutation in the BRCA gene:

   The total number of females is $3 \times 10^7$.

   The fraction of females with a mutation is given as 1 in 400, so:

   $\text{Number with mutation} = \frac{3 \times 10^7}{400} = 7.5 \times 10^4$.

2. Calculate the number likely to develop breast cancer:

   Given that 60% of women with this mutation are likely to develop breast cancer:

   $\text{Number likely to develop} = 0.6 \times 7.5 \times 10^4 = 4.5 \times 10^4$.

3. Therefore, the answer in standard form is:

   $4.5 \times 10^4$.

Operating to remove a brain tumour can produce side effects for several reasons:

1. Proximity to Critical Structures: The brain is a vital organ containing many critical structures, including neurons that control bodily functions. Surgery may inadvertently damage these structures, leading to side effects.

2. Swelling and Inflammation: Post-surgery inflammation can cause swelling in the brain, which might lead to increased pressure and various neurological complications.

3. Neurological Deficits: Depending on the tumor's location, removal might result in changes in cognitive function, movement, speech, or sensory perception, leading to long-term or permanent deficits.

In summary, one possible side effect could be neurological deficits resulting from damage to surrounding brain tissue.