CAMPBELL BIOLOGY IN FOCUS URRY CAIN WASSERMAN MINORSKY
CAMPBELL BIOLOGY IN FOCUS URRY • CAIN • WASSERMAN • MINORSKY • REECE 9 The Cell Cycle Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge, Simon Fraser University © 2016 Pearson Education, Inc. SECOND EDITION
Overview: The Key Roles of Cell Division § The continuity of life is based on the reproduction of cells, called cell division or mitosis § The process by which a single parent cell divides to become 2 identical daughter cells § Prokaryotic cells divide by binary fission (which is mitosis in bacteria). § Eukaryotic cells divide by mitosis and cytokinesis © 2016 Pearson Education, Inc.
Mitotic Cell Division Genetic make -up of an organism Eukaryotes Prokaryotes Genome large and linear Genome small and circular DNA in nucleus DNA in nucleoid region of cytoplasm Eukaryotic cells divide by mitosis (nuclear division) and cytokinesis (cytoplasmic division). Together known as mitotic cell division. Functions: • Reproduction of cells • Growth & development • Tissue renewal
Figure 9. 2 100 m (a) Reproduction 50 m (b) Growth and development Functions of Mitosis 20 m © 2016 Pearson Education, Inc. (c) Tissue renewal
THE HUMAN LIFE CYCLE • Multicellular adults: diploid • 2 n = 46, total number chromosomes in humans • Exception: reproductive cells (gametes) in testes and ovaries • Sperm & egg: each is haploid, n = 23
Chromosomes and Chromatin • Chromosomes – Thread-like structures in eukaryotic nuclei that package your genes – – Chemically made of 40% DNA & 60% histone proteins Visible only during mitosis & meiosis Each species has a characteristic # Human somatic/body cells: 46 total (23 prs) • 22 pr homologous chromosomes • 1 pr sex chromosomes – Human gametes: 23 only • Chromatin – Long, thinner fiber that shortens to become chromosome – Occurs long and thin during Interphase – Same as chromosome, but not visible
Figure 9. 3 Chromatin 20 m © 2016 Pearson Education, Inc.
Karyotype of Chromosomes • Photomicrograph of somatic cell metaphase chromosomes
Distribution of Chromosomes During Eukaryotic Cell Division § In preparation for cell division, DNA is replicated and the chromosomes condense/shorten § Each duplicated chromosome has two sister chromatids, joined identical copies of the original chromosome § The centromere is where the two chromatids are most closely attached Sister chromatids Centromere © 2016 Pearson Education, Inc.
Figure 9. 5 -s 3 Chromosomes Chromosomal DNA molecules Centromere Chromosome arm Chromosome duplication Sister chromatids Separation of sister chromatids © 2016 Pearson Education, Inc.
Cell Cycle (Eukaryotes) A generation of the cell: • M phase: mitosis and cytokinesis • Alternates with Interphase • G 1 phase • S phase • G 2 phase • G 0 phase • With few exceptions (RBC), most cells undergo cell cycle • Duration varies with cell type • Many repetitions of cell growth 20 – 50 x
Interphase: 90% of cell cycle: growth & metabolic activities • G 1 phase: preparation for DNA synthesis • S phase: DNA synthesis into sister chromatids • G 2 phase: preparation for M and C • G 0 phase: cells not actively dividing (either permanently- brain, nerves, skeletal muscles or cardiac muscles; or temporarily- liver)
Figure 9. 6 INTERPHASE S (DNA synthesis) G 1 ito M t y MIT C OTI (M) PHA C SE si in k o © 2016 Pearson Education, Inc. s is s e G 2
Figure 9. UN 02 Cell Cycle and Mitotic Phases INTERPHA SE G 1 Cytokinesis Mitosis S G 2 MITOTIC (M) PHASE Prophase Telophase and Cytokinesis Prometaphase Anaphase Metaphase Mitotic Phases: PPMAT/C © 2016 Pearson Education, Inc.
10 m Figure 9. 7 -1 G 2 of Interphase Centrosomes (with centriole pairs) Chromosomes (duplicated, uncondensed) Nucleolus Nuclear envelope © 2016 Pearson Education, Inc. Plasma membrane Prophase Early mitotic Centromere spindle Aster Two sister chromatids of one chromosome Prometaphase Fragments of nuclear envelope Kinetochore Nonkinetochore microtubules Kinetochore microtubules
10 m Figure 9. 7 -2 Metaphase Spindle Anaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Centrosome at one spindle pole Nuclear envelope forming © 2016 Pearson Education, Inc. Daughter chromosomes Nucleolus forming
Figure 9. 7 -3 G 2 of Interphase Centrosomes (with centriole pairs) Chromosomes (duplicated, uncondensed) Nucleolus Nuclear envelope © 2016 Pearson Education, Inc. Plasma membrane Prophase Early mitotic Centromere spindle Aster Two sister chromatids of one chromosome
Figure 9. 8 Aster Sister chromatids Centrosome Metaphase plate (imaginary) Kinetochores Microtubules Chromosomes Overlapping nonkinetochore microtubules Kinetochore microtubules 1 m 0. 5 m © 2016 Pearson Education, Inc. Centrosome
Figure 9. 7 -4 Prometaphase Fragments of nuclear envelope Kinetochore © 2016 Pearson Education, Inc. Metaphase Nonkinetochore microtubules Kinetochore microtubules Metaphase plate Spindle Centrosome at one spindle pole
Figure 9. 7 -5 Anaphase Telophase and Cytokinesis Cleavage furrow Daughter chromosomes © 2016 Pearson Education, Inc. Nuclear envelope forming Nucleolus forming
Figure 9. 11 Nucleus Chromosomes Nucleolus condensing Chromosomes 10 m Prometaphase Cell plate Prophase Metaphase © 2016 Pearson Education, Inc. Anaphase Telophase
Figure 9. 9 -2 Results Conclusion Chromosome movement Microtubule Motor protein Chromosome © 2016 Pearson Education, Inc. Kinetochore Tubulin subunits
Figure 9. 10 Cytokinesis (a) Cleavage of an animal cell (SEM) Cleavage furrow Contractile ring of microfilaments © 2016 Pearson Education, Inc. 100 m Daughter cells (b) Cell plate formation in a plant cell (TEM) Vesicles Wall of forming parent cell Cell cell plate 1 m New cell wall Daughter cells
Figure 9. 12 -s 4 Binary Fission in Prokaryotes Origin of replication Chromosome replication begins. One copy of the origin is now at each end of the cell. Replication finishes. Two daughter cells result. © 2016 Pearson Education, Inc. E. coli cell Two copies of origin Origin Cell wall Plasma membrane Bacterial chromosome Origin
Checkpoints of the Cell Cycle Control System § The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a timing device of a washing machine § The cell cycle control system is regulated by both internal and external controls § The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received © 2016 Pearson Education, Inc.
Figure 9. 15 G 1 checkpoint seems G 1 checkpoint to be the most important Control system G 1 M G 2 M checkpoint G 2 checkpoint © 2016 Pearson Education, Inc. S
Figure 9. 16 -1 G 1 Checkpoint G 1 checkpoint G 0 G 1 Without go-ahead signal, cell enters G 0. G 1 With go-ahead signal, cell continues cell cycle. (a) G 1 checkpoint If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G 0 phase © 2016 Pearson Education, Inc.
Figure 9. 16 -2 G 2 and M Checkpoints G 1 M G 2 M checkpoint Anaphase Prometaphase Without full chromosome attachment, stop signal is received. G 2 checkpoint Metaphase With full chromosome attachment, go-ahead signal is received. (b) M checkpoint Anaphase does not begin if any kinetochores remain unattached © 2016 Pearson Education, Inc.
Density-Dependent Inhibition § An example of an external signal is densitydependent inhibition, in which crowded cells stop dividing § Most animal cells also exhibit anchorage dependence, in which they must be attached to a substratum in order to divide § Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence © 2016 Pearson Education, Inc.
Figure 9. 18 Anchorage dependence: cells require a surface for division Density-dependent inhibition: cells form a single layer Density-dependent inhibition: cells divide to fill a gap and then stop 20 m (a) Normal mammalian cells © 2016 Pearson Education, Inc. 20 m (b) Cancer cells
Loss of Cell Cycle Controls in Cancer Cells § Cancer cells do not respond to signals that normally regulate the cell cycle § Cancer cells do not need growth factors to grow and divide § They make their own growth factor § They may convey a growth factor’s signal without the presence of the growth factor § They may have an abnormal cell cycle control system © 2016 Pearson Education, Inc.
Malignant Tumors are Cancer § Cancer cells that are not eliminated by the immune system form tumors or masses of abnormal cells within otherwise normal tissue § If abnormal cells remain only at the original site, the lump is called a benign tumor § A normal cell converted to a cancerous cell is called transformation § Malignant tumors invade surrounding tissues and undergo metastasis, exporting cancer cells to other parts of the body, where they may form additional tumors © 2016 Pearson Education, Inc.
5 m Figure 9. 19 Breast cancer cell (colorized SEM) Metastatic tumor Lymph vessel Tumor Blood vessel Cancer cell Glandular tissue A tumor grows from a single cancer cell. © 2016 Pearson Education, Inc. Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. A small percentage of cancer cells may metastasize to another part of the body.
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