cell growth & division - bay port biology - home€¦ · cell growth & division i. limits...
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January 2, 2019
Chapter 11
Cell Growth & Division
I. Limits to Cell Size> DNA Overload
– If cells get too big, don't have enough DNA to control the whole cell
> Surface Area to Volume Ratio– Can't exchange materials fast enough as they grow– Surface area cannot increase as fast as Volume
» More volume requires more material in/out
– So 1 cell divides into 2 to reduce volume* Cells require High Surface Area:Volume Ratio
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II. Types of Reproduction> Asexual Reproduction
– use of cell division to create genetically identical offspring from a single parent
» Simple, Efficient, Fast
> Sexual Reproduction– fusion of two parent cells (1/2 original DNA) to create 1
offspring cell with DNA from both parents» Produces Variation!
III. DNA Terms
> Chromatids: strands of DNA making up chromosomes– after copied, 2 copies are known as SISTER Chromatids
» If attached = 1 Chromosome
> Chromatin: DNA & Proteins– Loosely Coiled, able to read
> Chromosome: Condensed DNA & Proteins– Tightly Coiled, unable to read,
but easy to move
> Centromere: area where chromatids attach to each other
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– cell grows, prepares for division, & divides into 2 daughter cells
> Prokaryotes perform Binary Fission– simple & fast– Purpose
»
> Eukaryotes have a more complex Cell Cycle– Purpose
»
IV. Cell Cycle
M Phase
Mitosis Cytokinesis
Reproduction
Repair & Growth
Interphase
M Phase
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V. Interphase
> G1- Cell Growth
> S - Synthesize New DNA– (DNA Replication)
> G2- Cell Growth, Prepare for Cell Division
VI. Mitosis (PMAT)A) Prophase
> Chromatin Condenses into Chromosomes– Ultra Dense chromosomes now visible
> Centrioles separate– Spindles begin to form & attach to the centromeres
on chromosomes
> Nuclear membrane & Nucleolus break down
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VI. Mitosis (PMAT)B) Metaphase
> Sister chromatids line up along the middle of the cell
> Each chromatids are connected to the spindle fiber at their centromere
VI. Mitosis (PMAT)C) Anaphase
> Sister Chromatids separate into individual chromosomes– migrate to opposite
poles
> Chromatids "eat" their way down spindle fibers
> Spindle fibers connected to each other push
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VI. Mitosis (PMAT)D) Telophase
> Chromosomes migrated to each end
> Chromosomes loosen up into chromatin
> Nuclear membrane & nucleolus form
* Cytokinesis Occurs during the end of Telophase
VII. Cytokinesis> Cytoplasm divides
– Clevage furrow in animals– Cell plate in plants
> Each daughter cell has an identical set of duplicate chromosomes
> Chromosomes are no longer visible– in chromatin form
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VIII. Cell Cycle Summary
CELL CYCLE> 1 parent cell divides into 2 daughter cells
> allows for growth & development AND repair
> mitosis occurs in tissues thatrequire new cells continuously
such as skin cells, hairfollicles, lining of digestivetract, & in a newly fertilizedegg
Onion Root Tip Observation
• Root tips useful to study..> cells are frequently
dividing as the root grows
• Examine root tip> Find, Identify & Draw
Interphase and the 4 phases of mitosis on your hand out
> Fill in the missing information on the hand out using your notes
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IX. Cell Cycle Extras• Regulation
> Cyclin Proteins speed up & slow down cell cycle when needed– When injured, Growth Factors increase speed of
cell cycle
• Cancer> When errors in regulation cause cell cycle to continue
unregulated
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X. Cell Differentiation> A cell becomes a specialized cell by reading specific
portions of DNA
• Stem Cells:> Cells that have the ability to develop into any type of
cell» Able to access all DNA