Cell Cycle and Mitosis

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Cell Cycle and Mitosis
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Cell Cycle and Mitosis Cell Division process by
which a cell divides into 2 new cells
2 Daughter Cells
Parent Cell

• The original cell is called the parent cell 2
  new cells are called daughter cells

2 Daughter Cells
Parent Cell
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Why do cells need to divide?

• Living things grow by producing more cells, NOT
  because each cell increases in size
• Repair of damaged tissue
• If cell gets too big, it cannot get enough
  nutrients into the cell and wastes out of the
  cell

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Do you remember?

• 1) Which cell organelle controls all cell
  functions?
• 2) What does this cell organelle contain?
• 3) What do ALL cells need in order to have the
  directions/code to perform functions correctly?

Nucleus
Genetic Information
DNA
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• DNA
• DNA is located in the nucleus and controls all
  cell activities including cell division
• Long and thread-like DNA in a non-dividing cell
  is called chromatin
• Doubled, coiled, short DNA in a dividing cell is
  called chromosome
• Consists of 2 parts chromatid and centromere

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Compare and Illustrate DNA

• DNA in NON-DIVIDING Cell

• DNA in a DIVIDING Cell

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• Chromatin to chromosomes illustration

Chromatin
Coils up into chromosomes
Duplicates itself
Why does DNA need to change from chromatin to
chromosome?
More efficient division
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• 2 identical sister chromatids attached at
  an area in the middle called a centromere
• When cells divide, sister chromatids separate
  and 1 goes to each new cell

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Cell Cycle and Mitosis

• Before cell division occurs , the cell replicates
  (copies) all of its DNA, so each daughter cell
  gets complete set of genetic information from
  parent cell
• Each daughter cell is exactly like the parent
  cell same kind and number of chromosomes as the
  original cell

• Every organism has its own specific number of
  chromosomes
• Examples Human 46 chromosomes or 23
  pairs
• Dog 78
  chromosomes or 39 pairs
• Goldfish 94
  chromosomes or 47 pairs
• Lettuce 18
  chromosomes or 9 pairs

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• All somatic (body) cells in an organism have the
  same kind and number of chromosomes.
• Examples Human 46 chromosomes
• Human skin cell 46
  chromosomes
• Human heart cell 46
  chromosomes
• Human muscle cell 46
  chromosomes
• Fruit fly 8 chromosomes
• Fruit fly skin cell 8 chromosomes
• Fruit fly heart cell 8 chromosomes
• Fruit fly muscle cell 8 chromosomes

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• Cell Cycle -- series of events cells go through
  as they grow and divide
• Cell grows, prepares for division, then divides
  to form 2 daughter cells each of which then
  begins the cycle again

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Cell Cycle Outline

• Interphase
• G1 Cell Grows
• S DNA Replicates
• G2 Growth prepares for division
• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

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Cell Cycle and Mitosis
Get a friend and create a sentence to help you
remember the order of the cell cycle and mitosis.
Use the first letter of each term.

• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

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Interphase

• Interesting things happen!
• Cell preparing to divide
• Genetic material doubles
• Cells most of their time in Interphase

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Mitosis BeginsProphase, Metaphase, Anaphase,
Telephase

• Mitosis division of the nucleus into 2 nuclei,
  each with the same number of chromosomes
• Mitosis occurs in all the somatic (body) cells

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Prophase

• Chromosome pair up!
• Chromosomes become visible
• Nuclear membrane disappears
• Spindle fibers form

Prophase
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Metaphase

• Chromosomes meet in the middle!
• Spindle Fibers connect to chromosomes

Metaphase
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Anaphase
Anaphase

• Chromosomes get pulled apart
• Spindle fibers pull chromosomes to opposite sides

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Telophase

• Now there are two!
• Chromosomes uncoil
• Spindle fibers disappear
• Two nuclei are formed

Telophase
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Cytokinesis

Cytokinesis the division of the rest of the
cell (cytoplasm and organelles) after the nucleus
divides
In animal cells the cytoplasm pinches in In
plant cells a cell plate forms

• After mitosis and cytokinesis, the cell returns
  to Interphase to continue to grow and perform
  regular cell activities

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Mitosis is a type of asexual reproduction.

• There are two types of reproduction

Asexual Reproduction
Sexual Reproduction

• parent reproduces by itself
• offspring is genetically identical to mamma

• Offspring is genetically unique
• creates diversity within population

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Asexual Reproduction

• Mitosis
• Binary Fission
• Budding
• Spores
• Regeneration
• Vegetative Propagation

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1) Mitosis
2) Binary Fission

• a parent cell splits into 2 daughter cells of
  size
• w/ prokaryotes

• produce 2 identical daughter cells with the same
  of chromosomes as the parent cell. (identical)

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3) Budding
4) Spores

• spores are surrounded by a tough coat to help
  them survive harsh conditions. .. Produced and
  released

• a new, duplicate organism forms at the side of
  the parent and enlarges until an individual is
  created.

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5) Regeneration
6) Vegetative Propagation

• growth of new tissues/organs to replace those
  injured or lost.
• Common in invertebrates, especially Asteroidea
  (Sea Stars) and Annelida (Worms).

In some multicellular plants new plants
develop from the roots, stems, or leaves of the
parent.
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Sexual Reproduction

• Meiosis

Cell division that results in haploid gametes
used for sexual reproduction
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Haploid?

• When a gamete (sperm or egg) of an organism has
  HALF of the full amount of chromosomes
• Hap Half
• Remember, human cells have 46 chromosomes? Then
  the haploid is 23

• Sperm

• Egg

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Meiosis

• Occurs in the same four phases as mitosis but in
  two steps Meiosis I and Meiosis II

• Meiosis I
• All chromosomes make copes of themselves
• This doubles the of chromosomes in the cell

• Meiosis II
• Begins in same two cells created by Meiosis I
• Creates FOUR new haploid cells
• Occurs in a manner very similar to mitosis

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Outline of Meiosis

• Meiosis I
• Prophase I
• Metaphase I
• Anaphase I
• Telophase I
• Meiosis II
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II

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Prophase I

• Homologous chromosomes from each parent pair up!
• They form two attached sets of chromatids called
  a tetrad
• There are MANY ways the chromatids can line up
  this is one source of genetic variation.

• Homologous chromosomes
• 1 from each parent
• carry genes that control the same
• inherited traits.

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Metaphase I

• Each tetrad meets in the middle!
• Spindle fibers connect centromeres
• Crossing over of chromosomes may occur to provide
  additional genetic variation 2nd source of
  genetic variation

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Anaphase I

• Tetrads get pulled apart
• Homologous chromosomes move to opposite ends

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Telophase I

• Cells may finish cytokinesis OR proceed
  immediately with Meiosis II

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Prophase II

• Chromosomes did NOT replicate
• At this point, the cell is haploid because it no
  longer has one of every kind of chromosome that
  was in the original cell

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Metaphase II

• Sister chromatids line up on individual spindle
  fibers

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Anaphase II

• Sister chromatids are separated into each new
  cell
• Each new cell now has only HALF as many
  chromosomes as the parent cell in Prophase I

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Telophase II

• Each of the four new cells completes reforming
  nuclei and cytokinesis separates the four new
  hapliod cells

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How does meiosis lead to genetic variation?

• Look back at Prophase I Metaphase I, what may
  lead to genetic variation?
• There are MANY ways the chromatids can line up
• Crossing over of chromosomes may occur
• What is another factor that could lead to genetic
  variation?
• Random combinations of sperm and eggs

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Interphase
Interphase
Prophase 1
Review!
Metaphase 1
Meiosis 1
Anaphase 1
Telophase 1
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Prophase 2
Metaphase 2
Meiosis 2
Anaphase 2
Cytokinesis
Cytokinesis
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Note..
Male gametes
4 haploid gametes 4 sperm by way of
spermatogenesis
Female gametes
4 haploid gametes 1 Ovum (egg) 3 Polar
Bodies by way of oogenesis
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Sometimes cell division doesnt go as planned
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Cell Division Regulation

• Internal and external factors regulate cell
  division.

• Cancer is the uncontrolled growth and division of
  cells.
• Cancer cells can kill an organism by crowding out
  normal cells, resulting in the loss of tissue
  function.

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Cancer

• Benign cancer cells typically remain clustered
  together

• Malignant cancer cells can break away or
  metastasize

metastasize
Benign
Malignant
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Causes of Cancer

• Internal Factors
• Inheritance
• Mutations

Skin Cancer

• External Factors
• Carcinogens are substances that are known to
  produce and promote the development of cancer.
• Radiation
• Chemical
• Viruses

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Nondisjunction Mutations

• Improper separation of sister chromatids may
  result in a cell having one too many chromosomes
  (trisomy) or not having one of a certain
  chromosome (monosomy)

Karyotype a picture of an individuals
chromosomes so that the types of mutations might
be seen
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Trisomy 21 Down Syndrome
Trisomy 18 - Edward's Syndrome
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Meiosis Square Dance