The Cell Cycle. Genetic Information b Genome: cell’s genetic information b DNA organized into...
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Transcript of The Cell Cycle. Genetic Information b Genome: cell’s genetic information b DNA organized into...
![Page 1: The Cell Cycle. Genetic Information b Genome: cell’s genetic information b DNA organized into chromosomes Diploid (2n): 2 sets of chromosomes … somatic.](https://reader036.fdocuments.net/reader036/viewer/2022062516/56649e355503460f94b23a78/html5/thumbnails/1.jpg)
The Cell Cycle
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Genetic Information Genome: cell’s genetic
information DNA organized into
chromosomes• Diploid (2n): 2 sets of
chromosomes … somatic (body) cells
• Haploid (1n): 1 set of chromosomes… gametes (sex cells]
Sex Chromosomes – determine the sex of an organism
Autosomes- carry traits; not linked to sex
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Chromosomes
Before cells divide, their DNA coils up tightly into chromosomes
Chromatin: DNA-protein complex that makes up chromosomes
Chromatids: replicated strands of a chromosome
Centromere: narrowing “waist” of sister chromatids
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Functions of Cell Division
Unicellular reproduction Growth/Development Renewal/Repair
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The Cell Cycle
Interphase (90% of
cycle) • G1 phase~ growth
• S phase~ synthesis
of DNA • G2 phase~
preparation for cell division
Mitotic phase• Mitosis~ nuclear
division • Cytokinesis~
cytoplasm division
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Interphase
Growth 1 (G1)• Cell grows
Synthesis (S)• DNA replicates
Growth 2 (G2)• Cell grows and
prepares to divide
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Mitotic Spindle
Spindle fibers (microtubules) originate from the centrosome• Some animal cells contain
centrioles Aster- short array of
microtubules that extend from centrosome
Kinetochore- protein structure on chromosomes that microtubules attach to
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Mitosis
Prophase Prometaphase Metaphase Anaphase Telophase
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Prophase
Chromosomes visible
Nucleoli disappear
Sister chromatids Mitotic spindle
forms Centrosomes
move to opposite ends of cell
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Prometaphase
Nuclear membrane fragments
Spindle interaction with chromosomes
Kinetochore develops
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Metaphase
Centrosomes at opposite poles
Centromeres are aligned
Kinetochores of sister chromatids attached to microtubules (spindle)
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Anaphase
Paired centromeres separate; sister chromatids liberated
Spindle fibers shorten at the kinetochore end
Chromosomes move to opposite poles
Each pole now has a complete set of chromosomes
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Telophase/Cytokinesis
Telophase• Daughter nuclei form• Nuclear envelopes
arise• Chromatin becomes
less coiled• Two new nuclei
complete mitosis Cytokinesis
• Cytoplasmic division
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Plant and Animal Cytokinesis
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Plant Mitosis
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Bacteria Division
Prokaryotes divide by binary fission• Chromosome
duplicates• Cell grows• Membrane
pinches inward• Two identical
cells result
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Evolution of Mitosis
The “missing links” between prokayrotic binary fission and eukaryotic mitosis
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How do they know when to split?
Cell cycle has a control system
Cells pass through “checkpoints” • “Go-ahead” signal
cell continues to copy DNA and divide
• No signal cell leaves cell cycle and enters into G0 phase (no growth occurs)
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Chemical Controls
Protein kinases activate or deactivate cells• “Stop” and “go”
signals To be active,
kinases must be attached to a cyclin (Cdks)• MPF (maturation –
promoting factor)~ triggers M-phase
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Keeping Division in Check
Growth factors• Protein that
stimulates cells to divide
Density-dependent inhibition• Crowded cells stop
dividing Anchorage
dependence• Cells must attach
to a substrate to divide
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Dividing Cells Gone Wild Transformation of single cell
• If not destroyed, will reproduce and form a mass of cells (tumor)
Benign or malignant• If cells don’t spread benign• Malignant tumors spread and/or damage major
organs Metastasis
• Spread of cells from original site • Through lymph and blood vessels