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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January 2, 2019

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