Unit 1.6 Cell Division

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Unit 1.6 Cell Division
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Requirements for Cell DivisionBioflix Mitosis

• Receipt of a cell signal to direct the cell to
  divide
• 2. DNA replication
• 3. MitosisDNA distribution to identical nuclei.
• 4. Cytokinesis

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Which of the following are differences between
cell division and mitosis?

• A Mitosis require DNA replication but cell
  division does not.
• B Cell division includes cytokinesis but mitosis
  only includes nuclear division.
• C Neither cell division nor mitosis occurs in
  plant cells.
• D Mitosis is part of interphase but cell
  division happens after interphase.

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Uncoiled DNA in eukaryotic and prokaryotic cells.
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Note the difference between chromosomes and
chromatin. Do you understand how the different
structure attests to the different functions?
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HHMI DNA Packaging (Movie on website-Too big to
embed in the PPT)
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After DNA replication, the DNA tightly coils
into a chromosome.
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After replication each chromosome consists of two
identical DNA molecules (called chromatids) that
can be distributed into two different cells
Identical
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Prior to DNA replication, there are _____
chromosomes in a pair. After DNA replication,
there are ______ chromosomes in a pair.

• A 2, 2
• B 2, 4
• C 1, 2
• D 1, 4

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Identical chromatids

• A are 2 different chromosomes attached to each
  other.
• B are exact copies of one DNA molecule that are
  attached to each other.
• C arise from the ribosomes.
• D are broken down by lysosomes.
• E are chromosomes that carry different genes.

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Cell cycle composed of interphase, mitosis and
cytokinesis.

• Interphase has three distinct phases
• G1 cell growth and differentiation
• S synthesis and replication of chromosomes.
• G2 synthesis of molecules, other than DNA,
  needed for cell division.
• G0 Cells that never divide, such as nerve cells

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Which of the following occurs with DNA during
interphase, mitosis and cytokinesis?

• A Divides by half each time the cell divides.
• B Doubles each time the cell divides.
• C Doubles first and then divides by half each
  time the cell divides.

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Mitosiswhy bother?

1. Embryonic development
2. Growth
3. Tissue repair
4. Asexual reproduction

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Asexual reproduction (via mitosis) and sexual
reproduction (meiosis and fertilization) are
different in that

• A) individuals reproducing asexually transmit
  100 of their genes to their progeny, whereas
  individuals reproducing sexually only transmit
  50.
• B) asexual reproduction produces offspring that
  are genetically identical to the parents, whereas
  sexual reproduction gives rise to genetically
  distinct offspring.
• C) asexual reproduction involves a single parent,
  whereas sexual reproduction involves two.
• D) asexual reproduction only requires mitosis,
  whereas sexual reproduction always involves
  meiosis.
• E) all of the above

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Mitosis equal distribution of DNA into daughter
cells

• 5 phases of mitosis
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase

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Overview of Mitosis

• Meanwhile, the cytoskeleton spindle forms and the
  nucleus dissolves.

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Early Prophase

• Chromosomes condense
•  
• Mitotic spindle grows out of the MTOC.
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• Centrosomes migrate towards the poles

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Later Prophase

• Nuclear envelope disintegrates
• Spindle fibers attach to the chromosomes

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Centrosomes
Mitotic spindle
Microtubule
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Nuclear envelope breaking up
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Metaphase

• The centromere-spindle complexes align in the
  equator of the cell.

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Spindle microtubules
46 replicated chromosomes
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Spindle microtubules from opposite pole
Spindle microtubules from one pole
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46 chromosomes line up in center of cell
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Anaphase

• Chromatid separation.
• Identical DNA molecules move towards opposite
  poles

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Chromatid disjunction identical DNA molecules
(chromatids) are pulled apart
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Spindle fibers from one pole attached to DNA
molecule
Spindle fibers from opposite pole attached to
identical DNA molecule
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Telophase

• Nuclear envelope reforms.
• Spindle disappears.
• DNA reverts to chromatin
• Nucleolus reforms.

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46 DNA molecules
Pole
Pole
46 DNA molecules
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46 identical chromosomes in each cell!
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Nuclear envelopes
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Identical daughter cells
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Describe the events that occur in the four phases
of mitosis.
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Mitotic Spindle

• Three types of microtubules
• Kinetochore attach to each chromatid
• Polar or Non-kinetochore overlap with each other
• Astral attach the centrosome to the cell pole

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Cytokinesis is different in animal and plant
cells.
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Starting with a fertilized egg (zygote), a series
of five cell divisions (mitosis) would produce an
early embryo with how many cells?

• A) 4
• B) 8
• C) 16
• D) 32
• E) 64

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Progression through the cell cycle is controlled
by proteins.
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Cyclins family of proteins that activate a
kinase that allows cell cycle to proceed.
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Progression past G2 is controlled by interaction
between cyclin-dependent kinases (CDK) and
cyclins.
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All cancer arises from one cell
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2 different errors in cell cycle genetic control
result in same uncontrolled growth of cancer
cellsOncogenes speed up cell division.Tumor
suppressor genes slow it down.
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Accumulation of mutation
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What is the name of the process by which cancer
cells break off of tumors and spread to other
parts of the body?

• A mutagenesis
• B metastasis
• C carcinogenesis
• D metamitosis
• E angiogenesis

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Metastasis of cancer cells due to loss of density
dependence/anchorage dependence.
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The following have been diagnosed with cancer

• A One of my parents
• B My sister or brother
• C My aunts or uncles
• D more than one of the above
• E none of the above

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Do you

• A. Smoke?
• B. Suntan during the winter?
• C. Each processed meats like cold cuts or
  hotdogs?
• D. Drink alcohol?
• E More than one of the above???

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Some cancer statistics from ACS, 2011
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Cancer diagnoses and deaths, 2011
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Smoking is a risk factor for which type(s) of
cancer?

• A Prostate
• B Skin
• C Breast
• D Lung
• E All of the above

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• What causes these mutations?
• Certain types of radiation
• Chemicals in cigarettes
• Diet
• Viruses
• Types of electromagnetic radiation
• Ultraviolet light
• Old age
• Inherited from parents

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Tumors (cancer) are the results of uncontrolled
cell division and that these can occur in any
organ or tissue

• Some tumors are benign (harmless)
• Warts
• Others are malignant and spread to other tissues
• Then it is called cancer
• Treatments
• Surgical removal
• Removal before the tumor gets bigger or spreads
• Chemotherapy
• The use of chemicals to destroy cells that are
  growing too rapidly.
• Also kills cells responsible for hair growth,
  cells of the digestive system and sperm producing
  cells
• Radiation therapy
• Using a nuclear radiation beam to burn all
  cells in an area