Question 1
Paper 2Medium16 marksFigure 1 shows possible chromosome outcomes in a eukaryotic species with a diploid chromosome number of 2n = 4. The parent nucleus has completed DNA replication before either pathway begins. Chromosomes of the same length are homologous; solid and dashed lines distinguish the two homologues in each pair. The central dot on each chromosome represents a centromere. Crossing-over is not shown.
State the number of chromosomes and the number of chromatids in the replicated parent nucleus in Figure 1.
Using Figure 1, compare the number of nuclei formed and the chromosome number per nucleus after mitosis and meiosis.
Explain the role of DNA replication before mitosis and meiosis, referring to chromatids and their separation during these processes.
Explain two processes by which meiosis can generate genetically different nuclei. Explain why nuclear division should be completed before cytokinesis.