CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION Copyright © 2009 Pearson Education, Inc.
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Transcript of CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION Copyright © 2009 Pearson Education, Inc.
CONNECTIONS BETWEEN CELL DIVISION AND
REPRODUCTION
Copyright © 2009 Pearson Education, Inc.
◦ Living organisms reproduce by two methods
– Asexual reproduction– Offspring are identical to the original cell or organism– Involves inheritance of all genes from one parent
– Sexual reproduction– Offspring are similar to parents, but show variations in
traits– Involves inheritance of unique sets of genes from two
parents
◦ What drives reproduction??? Cell division
Copyright © 2009 Pearson Education, Inc.
◦ Binary fission- “dividing in half”
– Two identical cells arise from one cell
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Prokaryoticchromosome
Duplication of chromosomeand separation of copies
Cell wall
Plasmamembrane
1
Continued elongation of thecell and movement of copies2
Division intotwo daughter cells
3
Two options:
– Mitosis: two genetically identical cells, with the same chromosome number as the original cell
– Meiosis: four genetically different cells, with half the chromosome number of the original cell
Eukaryotic cell divisionEukaryotic cell division
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Centromere
Chromosomeduplication
Sister chromatids
Chromosomedistribution
todaughter
cells
◦ Eukaryotic chromosomes are composed of chromatin
– Chromatin = DNA + proteins
– Early in the division process, chromosomes duplicate (sister chromatids)
– Sister chromatids are joined at centromere
Eukaryotic chromosomesEukaryotic chromosomes
MITOSIS:CELL “CLONING”
◦ The cell cycle is an ordered sequence of events for cell division
◦ It consists of two stages– Interphase: duplication of cell contents
– G1—growth, increase in cytoplasm– S—duplication of chromosomes– G2—growth, preparation for division
– Mitotic phase: division – Mitosis—division of the nucleus– Cytokinesis—division of cytoplasm
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S(DNA synthesis)G1
G2
Cytokinesis
Mito
sis
INTERPHASE
MITOTICPHASE (M)
◦ Mitosis progresses through a series of stages
1. Prophase2. Prometaphase3. Metaphase4. Anaphase5. Telophase (Cytokinesis
overlaps)
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◦ A mitotic spindle is required to divide the chromosomes
– The mitotic spindle is composed of ____________
– It is produced by centrosomes
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Centrosomes(with centriole pairs) Kinetochore
Early mitoticspindle
Chromatin
INTERPHASE PROMETAPHASEPROPHASE
Centrosome Fragmentsof nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Nuclearenvelope
Spindlemicrotubules
Nucleolus
Centromere
Metaphaseplate
Nucleolusforming
METAPHASE TELOPHASE AND CYTOKINESISANAPHASE
Cleavagefurrow
Daughterchromosomes
NuclearenvelopeformingSpindle
◦ Cytokinesis
– Cytoplasm is divided into separate cells
***Applying Your Knowledge
By the end of cytokinesis – How many chromosomes are present in one human
cell?– How many chromatids are present in one human
cell?
The final mitosis: The final mitosis: CytokinesisCytokinesis
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TELOPHASE AND CYTOKINESIS
Let’s review Let’s review mitosismitosis
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◦ Mitosis produces genetically identical cells for
– Growth– Replacement– Asexual reproduction
◦ Factors that control cell division
– Presence of essential nutrients
– Growth factors, proteins that stimulate division
– Presence of other cells causes density-dependent inhibition
– Contact with a solid surface; most cells show anchorage dependence
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Culture of cells
Addition ofgrowthfactor
Cells anchor todish surfaceand divide.
When cells haveformed a completesingle layer, theystop dividing (density-dependent inhibition).
If some cells arescraped away, theremaining cells divideto fill the dish with asingle layer and thenstop (density-dependent inhibition).
◦ Cell cycle control system– A set of molecules, including growth factors,
that triggers and coordinates events of the cell cycle
◦ Checkpoints – Control points where signals regulate the cell
cycle– G1 checkpoint allows entry into the S phase or
causes the cell to leave the cycle, entering a nondividing G0 phase
– G2 checkpoint
– M checkpoint
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G1 checkpoint
Controlsystem
M
S
G2
G1
M checkpoint
G2 checkpoint
G0
What happens when cells don’t What happens when cells don’t obey the checkpoints and obey the checkpoints and
control system?control system?
Why do we need to control cell Why do we need to control cell division?division?
– All cancers are genetic at their origin
– They divide rapidly, often in the absence of growth factors
– They often do not have density-dependent inhibition
– They are “immortal”
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◦ Classification of cancer by origin
– Carcinomas arise in external or internal body coverings
– Sarcomas arise in supportive and connective tissue
– Leukemias and lymphomas arise from blood-forming tissues
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Classification of cancer by origin
– Carcinomas arise in external or internal body coverings (ex. Basal cell carcinoma)
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Classification of cancer by origin
– Sarcomas arise in supportive and connective tissue (ex. Kaposi’s sarcoma)
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Classification of cancer by origin
– Leukemias and lymphomas arise from blood-forming tissues
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◦ Types– Benign tumors remain at the original site
– Malignant tumors spread to other locations by metastasis
Cancer Cancer terminologyterminology
A tumor grows from asingle cancer cell.
Cancer cells spreadthrough lymph andblood vessels toother parts of the body.
Cancer cells invadeneighboring tissue.
Tumor
Glandulartissue
Lymphvessels
Bloodvessel
