VOCABULARY: chromatid centromere interphase cell cycle mitosis

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VOCABULARYchromatidcentromereinterphasecell
cyclemitosis
8.2 Cell Growth and Reproduction
Nucleus
centriolespindle prophasemetaphaseanaphasetelo
phasecytokinesis
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• How big do you think the largest cell is?
• Yolk of ostrich egg 8cm in diameter
• Average cell size range from 2-200µm in diameter
• Why arent there more large cells like the
  ostrichs?

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When a living organism grows

• On average, the cells of an adult animal are the
  same size as those of a young animal
• So whats the difference between a young animal
  and adult animal?
• The difference is that there are a lot MORE cells
  in an adult animal!

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3 Factors Limiting Cell Size

• Diffusion
• DNA
• Surface Area-to-Volume Ratio
• Why do you think these factors would influence
  cell size?

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Diffusion as a limiting factor

• Rememberthe cell membrane allows for nutrients
  and gases to diffuse into and out of cell
• Diffusion is fast and efficient but only over
  short distances
• As distance increases, it becomes slow and
  inefficient

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DNA as Limiting Factor

• As a cell grows in size, more demands are placed
  on the
• cells DNA
• It takes time to make proteins that play a
  critical role in cell function
• Ex a small town library has enough books for
  people to borrow but if a lot of people move into
  the town, some people may have to wait for
  popular books DNA is like a genetic library

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Surface Area-to-Volume Ratio

• As cell increases in size, volume increases much
  faster than S.A.

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• In other words.if a cell size were to double in
  size, there would be 8 times more waste to get
  rid of!
• A cell cant get rid of wastes that quickly it
  would poison itself!
• The lower the SA/Volume ratio, the harder it is
  to get materials into/out of the cell

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The Cell Cycle
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3 main stages of the cell cycle

• Interphase longest stage preparation for cell
  division
• Mitosis nucleus divides into 2 nuclei, each with
  the same and kind of chromosomes (DNA) as the
  parent cell
• Cytokinesis cytoplasm divides forming 2 distinct
  cells

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Cell Cycle Overview

• Interphase quite long
• most of the cells time spent here
• Cell Division occurs quickly

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Parts of Interphase

• G1 phase cells GROW, make organelles and
  proteins perform their JOB(S)!...basically, they
  have a life!
• S phaseDNA is copied
• (S stands for SYNTHESIS!)
• G2 phase more organelles are produced than are
  needed in preparation for cell division

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MITOSIS

• MITOSIS division of the NUCLEUS

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Why is it so important that the nucleus divides
in mitosis?(for DNA to be copied and divided?)

• it stores the DNA (information of life)
• all new cells need this information

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Chromosomes

• Genetic information is passed on from one
  generation to the next through chromosomes

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Chromosomes

• Every organism has a specific number of
  chromosomes
• ex 1 carrots 18 chromosomes
• ex 2 humans 46 ? 23 came from MOM 23 came
  from DAD
• Chromosomes are not visible in most cells except
  in cell division

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Why are chromosomes only visible during cell
division?

• During interphase, the DNA and protein molecules
  that make up chromosomes is spread throughout the
  nucleus being used
• (a.k.a. CHROMATIN)

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• At the beginning of cell division, the
  chromosomes condense into compact visible
  structures (CHROMOSOMES)
• Before cell division (in the S phase of
  interphase), each chromosome is replicated
  (copied)
• Each chromosome is made up of 2 identical
  sister chromatids held together by a centromere
  

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chromosome
centromere
chromatin
DNA
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Mini-Summary (up to this point)

• During a cells life, its DNA is being used/
  giving instructions to make proteins
• Cell gets too big so the cell prepares to divide
• DNA replicates
• DNA condenses into visible structures
  (chromosomes)
• Chromosomes are now ready for division!

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Mitosis is one, continuous event, but it can be
described as happening in 4 phases

• Prophase
• Metaphase
• Anaphase
• Telophase

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Remember, the cell is coming out of Interphase
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PROPHASE

• chromatin condenses chromosomes become visible
• centrioles separate and move to opposite sides of
  the nucleus

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• Centrioles

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PROPHASE continued

• spindle fibers (from centrioles) connect to
  chromosomes at their centromeres
• nuclear envelope breaks down and the nucleolus
  disappears

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PROPHASE (early late)
LATE PROPHASE
EARLY PROPHASE
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METAPHASE

• chromosomes line up in the center of the cell
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• fibers connect from the poles (end) of the
  spindle to the centromere of each chromosome

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METAPHASE
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ANAPHASE

• centromeres split, causing the sister chromatids
  to separate, becoming individual chromosomes
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• individual chromosomes are pulled apart to
  opposite ends of the cell

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ANAPHASE
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TELOPHASE

• chromosomes uncoil into chromatin
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• new nuclear envelope forms around the chromatin
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• spindle breaks apart
•  
• nucleolus reappears in each new nucleus

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TELOPHASE
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Often, telophase overlaps with cytokinesis.
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CYTOKINESIS

• CYTOKINESIS division of the cytoplasm

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Finally CYTOKINESIS

• in animal cells cell membrane pinches in
  divides
• in plant cells a cell plate (new cell wall)
  forms

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Then each new cell returns to interphase and the
process continues
One More Time!
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PROPHASE
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METAPHASE
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ANAPHASE
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TELOPHASE
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Finally CYTOKINESIS
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and back to INTERPHASE
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