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Multiple Choice
Which two key events occur at the beginning of meiosis but not mitosis?
A
Cytokinesis and DNA replication
B
Synapsis and crossing over
C
Chromosome condensation and spindle formation
D
Nuclear envelope breakdown and centrosome duplication
Verified step by step guidance
1
Understand the basic difference between meiosis and mitosis: Meiosis is a type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell. Mitosis, on the other hand, results in two identical daughter cells with the same number of chromosomes as the parent cell.
Identify the unique events in meiosis: Meiosis includes two rounds of division, meiosis I and meiosis II. The key events that occur at the beginning of meiosis I but not in mitosis are synapsis and crossing over.
Explain synapsis: Synapsis is the pairing of homologous chromosomes during prophase I of meiosis. This process does not occur in mitosis, where homologous chromosomes do not pair up.
Explain crossing over: Crossing over is the exchange of genetic material between homologous chromosomes during synapsis. This leads to genetic variation in the gametes produced by meiosis. Crossing over does not occur in mitosis.
Conclude with the significance: The events of synapsis and crossing over are crucial for genetic diversity, which is a key advantage of sexual reproduction. These processes ensure that the gametes produced are genetically unique, contributing to variation in offspring.