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Multiple Choice
During prometaphase of meiosis I, how must spindle microtubules attach to chromosomes to ensure proper segregation?
A
Microtubules do not attach to chromosomes during prometaphase of meiosis I.
B
Each sister chromatid is attached to microtubules from opposite spindle poles (bipolar attachment of sister chromatids).
C
Both sister chromatids of a chromosome are attached to microtubules from the same spindle pole (monopolar attachment).
D
Each homologous chromosome is attached to microtubules from opposite spindle poles (bipolar attachment).
Verified step by step guidance
1
Understand the context of meiosis I: Meiosis I is the first division in meiosis, where homologous chromosomes (not sister chromatids) are separated into two daughter cells. This is different from mitosis, where sister chromatids are separated.
Focus on prometaphase of meiosis I: During prometaphase, the nuclear envelope breaks down, and spindle microtubules begin to interact with chromosomes. The attachment of microtubules to chromosomes is critical for proper segregation.
Recall the structure of chromosomes during meiosis I: Each homologous chromosome consists of two sister chromatids joined at the centromere. Homologous chromosomes are paired together in a structure called a bivalent or tetrad.
Determine the correct attachment: To ensure proper segregation, each homologous chromosome must be attached to microtubules from opposite spindle poles. This is known as bipolar attachment. This ensures that homologous chromosomes are pulled to opposite poles during anaphase I.
Eliminate incorrect options: Microtubules do attach to chromosomes during prometaphase. Bipolar attachment of sister chromatids occurs in mitosis, not meiosis I. Monopolar attachment of sister chromatids would not allow proper segregation of homologous chromosomes. Therefore, the correct attachment is bipolar attachment of homologous chromosomes.