KINE 1000 Lecture Notes - Lecture 8: Sister Chromatids, G1 Phase, G2 Phase
4 Jun 2018
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Chapter 17- The Cell Cycle
• Cycle of duplication & division is called cell cycle
• Cell cycle is required to produce functioning organisms to replace cells that die
• Most fundamental task is to pass genetic information to next generation of cells
& produce genetically daughter cells. DNA must be replicated to produce two
complete copies & must be distributed (segregated) into two daughter cells
• Dividing cells must coordinate growth w/ division
• Cell-cycle control system triggers different stages of events of cycle
• Extracellular signals govern rates of cell growth & division
Overview of Cell Cycle
• Chromosomes duplication occurs during S-phase (DNA synthesis) – 10-12 hours
• Chromosome segregation & cell division occur in M phase (Mitosis)
o Nuclear division (Mitosis)
o Cytoplasmic division (cytokinesis)
• Mitosis Stages:
o Prophase: condensation of chromosomes into sister chromatids which remain
linked by sister-chromatid cohesion
o Metaphase: sister chromatids are attached to opposite poles of spindles &
align at equator
o Anaphase: destruction of sister chromatid cohesion separates sister
chromatids
o Telophase: spindles disassemble & segregated chromosomes are packed into
separate nuclei
o Cytokinesis: cleaves cell into tow daughter cells
Eukaryotic Cell Cycle Consists of 4 Phases
• Gap Phases allow time for growth & monitor internal & external enviroment to
ensure conditions suitable
• G1 phase b/t M phase & S-phase; G2 phase b/t S phase & mitosis
• G1, S, G2 & M; G1, S, G2 → interphase (23 hours)
• Cell growth occurs through cycle except during mitosis (condensed)
• G1 Phase can be delayed if conditions unfavourable for DNA duplication.
• G ZERO is where cells remain before resuming proliferation
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