第八章 細胞分裂與有絲分裂 前言

chromosome (unduplicated) in a cell at interphase same chromosome (duplicated) in interphase prior to mitosis mitosis, cytoplasmic division Fig. 8.6, p. 131 chromosome (unduplicated) in a daughter cell at interphase chromosome (unduplicated) in a daughter cell at interphase

分裂的細胞: 世代間的橋樑 分裂機制的概觀 有關染色體的要點 有絲分裂與染色體的數目

細胞的分裂 有絲分裂 (Mitosis) vs. 減數分裂 (Meiosis) 體細胞 (Somatic cell) vs. 生殖細胞 (Germ cell)

Prokaryotic organisms Division Mechanisms Eukaryotic organisms Mitosis Meiosis Prokaryotic organisms Prokaryotic fission

Roles of Mitosis Multicelled organisms Growth Cell replacement Some protistans, fungi, plants, animals Asexual reproduction

細看染色體 姊妹染色分體 著絲粒

Organization of Chromosomes DNA one nucleosome DNA and proteins arranged as cylindrical fiber histone

One nucleosome DNA core of histone Fig. 8.3, p. 129

單套 (Haploid) vs. 雙套 (Diploid) 有絲分裂與染色體的數目 單套 (Haploid) vs. 雙套 (Diploid) Sum total of chromosomes in a cell Somatic cells Chromosome number is diploid (2n) Two of each type of chromosome Gametes Chromosome number is haploid (n) One of each chromosome type

Human Chromosome Number Diploid chromosome number (n) = 46 Two sets of 23 chromosomes each One set from father One set from mother Mitosis produces cells with 46 chromosomes--two of each type

Lots of DNA Stretched out, the DNA from one human somatic cell would be more than two meters long A single line of DNA from a salamander cell would extend for ten meters

細胞週期 (Cell Cycle)

Spindle Apparatus one spindle pole one of the condensed chromosomes spindle equator microtubules organized as a spindle apparatus one spindle pole

Interphase Usually longest part of the cycle Cell increases in mass Number of cytoplasmic components doubles DNA is duplicated

Stages of Interphase G1 S G2 Interval or gap after cell division Time of DNA synthesis (replication) G2 Interval or gap after DNA replication

Control of the Cycle Once S begins, the cycle automatically runs through G2 and mitosis The cycle has a built-in molecular brake in G1 Cancer involves a loss of control over the cycle, malfunction of the “brakes”

Stopping the Cycle Some cells normally stop in interphase Neurons in human brain Arrested cells do not divide Adverse conditions can stop cycle Nutrient-deprived amoebas get stuck in interphase

有絲分裂之階段 前期 (Prophase) 中期 (Metaphase) 後期 (Anaphase) 末期 (Telophase)

前期:有絲分裂之開始

過度到中期 後期到末期

胞質分裂 (Cytokinesis; Cytoplasmic division) 植物有細胞板的形成 動物細胞的胞質分裂

植物: 細胞板 (Cell plate) 的形成

動物細胞的胞質分裂 分割溝 (Cleavage furrow)

Culturing Cells Growing cells in culture allows researchers to investigate processes and test treatments without danger to patients Most cells cannot be grown in culture