Question

in both mitosis and meiosis, ____________ must occur for the process to continue to completion.
a crossing over
b reduction division
c chromosome replication
d homologous chromosomes form tetrads

Explanation:

• Option A: Crossing - over occurs only in meiosis (prophase I) and not in mitosis.
• Option B: Reduction division (where chromosome number is halved) occurs only in meiosis (meiosis I) and not in mitosis.
• Option C: Both mitosis and meiosis require chromosome replication (during the S - phase of the cell cycle) before the division process can start. In mitosis, it ensures that the two daughter cells get the same genetic material as the parent cell. In meiosis, it is the starting point for the two - stage division process where genetic material is distributed to gametes.
• Option D: Homologous chromosomes forming tetrads (synapsis) occurs only in meiosis (prophase I) and not in mitosis.

Answer:

C. chromosome replication