OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What do spindle fibers do during stage 5 of meiosis?

1. Pull the cell membranes apart

2. Pull the chromosome arms apart

3. Attach to the nucleus

4. Facilitate DNA replication

The correct answer is: Pull the chromosome arms apart

During stage 5 of meiosis, known as anaphase II, spindle fibers play a crucial role in ensuring that the chromosomes are distributed correctly to the daughter cells. Specifically, spindle fibers pull the sister chromatids apart, which are the two identical halves of each chromosome formed during DNA replication. This action is vital as it ensures that each daughter cell ends up with an identical set of chromosomes. The process involves the spindle fibers, which are made up of microtubules and extend from the centrosomes, binding to the centromeres of the chromosomes. As they shorten, they exert a pulling force that separates the sister chromatids and drags them toward opposite poles of the cell. This separation is critical for genetic diversity and proper cell division, as it guarantees that each gamete receives the appropriate number of chromosomes. In this context, the other options do not accurately reflect the function of spindle fibers during this stage. For example, spindle fibers do not pull the cell membranes apart, attach to the nucleus, or facilitate DNA replication. Instead, their primary and essential role is to facilitate the separation and movement of chromosomes.