In women, the first division of meiosis produces one daughter cell that has almost all of the cytoplasm - AQA - A-Level Biology - Question 3 - 2018 - Paper 3

Tick the box next to 'Crossing over' as it is the process that results in genetic variation by exchanging parts of alleles between homologous chromosomes.

First, calculate the volume of the polar body using the formula for the volume of a sphere:

$V = \frac{4}{3} \times \tau r^3$

The radius of the polar body is: $\frac{10.4}{2} = 5.2$ µm.

Thus, the volume is:

$V = \frac{4}{3} \times 3.14 \times (5.2)^3 \approx 32.73 \: \text{µm}^3$

Next, calculate the number of mitochondria:

Number of mitochondria = Volume of polar body × Density of mitochondria

$= 32.73 imes 0.08 = 2.6184 \approx 2.62.$

Therefore, the estimated number of mitochondria in the polar body is approximately 2.

This treatment prevents the inheritance of mitochondrial diseases by ensuring that the egg cell receives a nucleus from a healthy donor. This replacement nucleus will contain normal genes, thus establishing a healthy mitochondrial population in the new egg, preventing the transmission of faulty mitochondria from the affected woman's polar body.

If most of the mitochondria in a cell are faulty, this leads to a significant decrease in ATP production. ATP is crucial for energy transfer in biological processes. A lack of ATP would hamper essential metabolic functions, leading to decreased energy availability for cellular processes.