Question 30

During meiosis I, the chromosome number is reduced from diploid to haploid.

This reduction occurs as a result of the separation of homologous chromosomes, which is a key feature of meiosis I.

A) S phase

The S phase is the part of interphase where DNA replication occurs, resulting in the duplication of chromosomes. However, there is no reduction in chromosome number during this phase; instead, the cell remains diploid.

B) interphase

Interphase encompasses the S phase, G1, and G2 phases, during which the cell prepares for division and duplicates its DNA. While crucial for the cell cycle, interphase does not involve the reduction of chromosome number from diploid to haploid.

C) mitosis

Mitosis is the process by which a diploid cell divides to produce two genetically identical diploid daughter cells. There is no reduction in chromosome number in mitosis; therefore, it does not answer the question regarding the transition from diploid to haploid.

D) meiosis I

Meiosis I is the correct phase where the chromosome number is reduced from diploid to haploid. During this stage, homologous chromosomes are segregated into different daughter cells, effectively halving the chromosome number.

Conclusion

Meiosis I is the definitive phase for reducing the chromosome number from diploid to haploid, distinguishing it from other phases such as S phase, interphase, and mitosis, which do not achieve this reduction. Therefore, option D is the only correct answer regarding the specific phase responsible for this chromosomal transition.