34.2
간기
세포 주기는 약 24시간(일반적인 인간 세포에서)에 걸쳐 발생하며 세포 주기의 세 단계(G1, S, G2)와 유사분열(M)을 포함하는 간기의 두 가지 별개 단계로 진행됩니다. 진핵세포 주기의 약 95%를 차지하는 간기 동안 세포는 유사분열을 준비하기 위해 성장하고 DN…
진핵 세포에서 세포주기의 가장 큰 부분은 간기이며 G1, S 및 G2의 3 단계로 나뉩니다.
첫 번째 갭 단계인 G1에서는 새로 생성된 딸세포의 크기가 커지고 다음 단계에서 DNA 복제를 준비합니다.
이제 합성 단계인 S에서 세포는 핵 DNA를 복제하고, 이 DNA는 염색질로 포장된 상태로 남아 있습니다. 세포는 또한 유사분열 방추체기구(mitotic spindle apparatus)를 형성하는 미세소관 조직 구조인 중심체(centrosomes)를 복제합니다.
마지막으로, 두 번째 갭 단계인 G2에서 세포는 계속 성장하여 유사분열에 필요한 소기관과 단백질을 증식시키고 에너지 저장을 보충합니다. 세포는 이제 유사분열의 첫 번째 단계로 들어갈 준비가 되었습니다.
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Q1: What are the three phases of interphase in eukaryotic cells?
Interphase consists of G1, S, and G2 phases. G1 is the first gap phase where cells grow and prepare for DNA duplication. S is the synthesis phase where DNA replication occurs. G2 is the second gap phase where cells continue growing and prepare for mitosis. Together, these phases comprise approximately 95 percent of the cell cycle.
Q2: What happens during the G1 phase of interphase?
During G1, newly generated daughter cells grow in size and prepare for DNA duplication. Cells are metabolically active, copying essential organelles and biochemical molecules such as proteins. The G1 phase typically spans approximately 11 hours in human cells, during which cells remain diploid with one copy of each chromosome.
Q3: How does DNA content change during the S phase?
During the S phase, cells duplicate their nuclear DNA, which remains packaged as chromatin. This DNA replication increases the cell's DNA content from 2n to 4n. Cells also duplicate the centrosome, a microtubule-organizing structure that forms the mitotic spindle apparatus. The S phase takes approximately 8 hours in human cells.
Q4: What is the role of the centrosome during interphase?
The centrosome is a microtubule-organizing structure that cells duplicate during the S phase of interphase. It forms the mitotic spindle apparatus, which separates chromosomes during mitosis. By duplicating the centrosome during interphase, cells ensure they have the necessary structures ready for the upcoming mitotic division.
Q5: What occurs during the G2 phase of interphase?
During G2, cells continue to grow and synthesize proteins and organelles required for mitosis. They replenish energy stores and prepare for the first stage of mitosis. The G2 phase typically lasts about 4 hours in human cells. After G2 completion, the cell is ready to enter mitosis.
Q6: How long does interphase last compared to the entire cell cycle?
Interphase takes up approximately 95 percent of the total cell cycle duration. In a typical human cell, the entire cell cycle occurs over approximately 24 hours, with G1 spanning about 11 hours, S phase taking about 8 hours, and G2 lasting about 4 hours. This leaves only about 1 hour for mitosis and cytokinesis.
Q7: When does DNA content return to 2n after interphase?
Following DNA replication in the S phase, cells increase their DNA content to 4n and remain at this level through G2 and mitosis. DNA content is reduced back to 2n only after cytokinesis is complete. Understanding the cell cycle helps clarify how cells prepare for division and maintain proper genetic content.