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Cell Division
Cell Division:
 Cell must divide because
 -They get too big due to cell
growth
 -Get injured and die
 -Get too old
 -to continue the species
 Two ways cells divide:
 1. Cell replacement and body
growth are accomplished by
mitosis and cytokinesis
 2. Sex cell production is
accomplished by meiosis.
Cell Cycle
 The cell cycle is an
ordered set of events,
culminating in cell growth
and division into two
daughter cells of body
(somatic) cells.
 Non-dividing cells not
considered to be in the
cell cycle (nerve cells
and muscle cells)
 Cell cycle is under control
of a special proteins called
cyclins:
Cell Cycle
Control of the Cell Cycle
 The stages are G1-S-G2-M.
 The G1 "GAP 1". Cell growth occurs
 The S stage "Synthesis". DNA replication
occurs.
 The G2 stage "GAP 2". Second cell growth
occurs to accommodate replicated organelles
from S stage
 G1, S and G2 occur during Interphase, the
longest stage of the cell cycle.
 M stage stands for "mitosis", and is when
nuclear (chromosomes separate)
 Finally, Cytokinesis: cytoplasmic division occur.
Mitosis is further divided into 4 phases.
Genetic Engineering
 DNA Extraction Lab
 Recombinant DNA
 Restriction Enzymes
 Gel Electrophoresis
Mitosis and Meiosis
 Mitosis and
Cytokinesis
 Stages of Meiosis
 Comparison of
Meiosis and Mitosis
 UNIQUE FEATURES
OF MEIOSIS
P-MAT
Interphase
Prophase
Anaphase
telophase
Metaphase
Cell plate
A
B
C
D
Interphase
E
Plant
Animal
Mitosis in Plants and Animal






Structure
Cell plate
Cleavage furrow
Mitotic spindles
Division begins in Anaphase
Disision begins in Telophase
Plants
yes
no
no
no
yes
Animals
no
yes
yes
yes
no
Lab: Plant Cell Mitosis
 Read each part carefully
 Start focusing in low power
 Change to medium power and focus using fine
adjustment knob
 Finally, change to high power and focus again
using the fine focus knob
 Draw one cell for each stage using pencil
 Answer questions for each section
 Do analysis question; Remember, it’s the most
important part of the lab!
Cellular senescence
 Cellular senescence is the phenomenon where cells lose
the ability to divide and cells begin to age.
 This is noticeable in our bodies as graying of hair,
wrinkling of skin, redistribution of body fat, etc…
Theories of Aging
Shortening of telomeres: Cells with
critically short telomeres become
senescent, unable to divide further, and
eventually malfunction. Some even die
Shortening occurs because of repeated
replication
Theories of Aging
Free Radicals:Free radicals are oxygen
molecules with unpaired electrons.
Free radicals damage cells in an
organism, causing aging.
Our bodies generate free
radicals in the mitochondria
during cellular respiration.
Anti oxidants can inhibit
production of free radicals
Antioxidants
 Can slow down aging and prevent
Cancer
 Antioxidants include: Vitamin C…
 Vitamin E…
 Selenium mineral
What about cloning human cells?
What Is Skin Cancer?
 An abnormal overgrowth (a tumor) of certain
types of skin cells in the epidermis that began as
normal skin structures.
 A tumor can be either benign (generally
localized and not life-threatening) or malignant
(invasive or spreading, and may be deadly).
 Skin cancer is a malignant tumor, able to invade
surrounding tissues and metastasize (or spread)
to other parts of the body, BUT…..
Federal Occupational Health
19
Melanoma
 A form of skin cancer that arises in melanocytes,
the cells that produce pigment and also are
found in the epidermis.
 Melanomas usually begin in a mole, which is a
benign cluster of melanocytes and other tissue.
Normal
moles:
Melanoma
 Melanoma is the deadliest form of skin
cancer, causing more than 75% of all skin
cancer deaths.
 About 53,600 people in the United States
were diagnosed with a melanoma skin.
cancer in 2002, and approximately 7,400
died from the disease.
Melanoma (the A-B-C and Ds)
Asymmetry -- The shape of one half does not
match the other.
Melanoma (the A-B-C and Ds)
Border -- The edges are often ragged, notched,
blurred, or irregular in outline; the pigment may
spread into the surrounding skin.
Melanoma (the A-B-C and Ds)
Color -- The color is uneven. Shades of black,
brown, and tan may be present. Areas of white,
grey, red, pink, or blue also may be seen.
Melanoma (the A-B-C and Ds)
Diameter -- There is a change in size, usually an
increase. Melanomas are usually larger than the
eraser of a pencil (5 mm or 1/4 inch).
Melanoma
May be found when a pre-existing mole
changes:
Early changes
- forming a new black area
- newly formed fine scales
- itching in a mole
More advanced changes
- texture changes (becomes hard or lumpy)
- itch, ooze, or bleed
- usually do not cause pain
Who is at risk for skin cancer?
Light skin color, hair color, eye color.
Family history of skin cancer.
Personal history of skin cancer.
Certain types and a large number of moles.
Freckles, which indicate sun sensitivity and sun
damage.
Chronic exposure to the sun.
History of sunburns early in life.
Sunburns are common
The Behavior Risk Factor Surveillance
System provided data showing nearly 32%
of all adults in the US report having had a
sunburn in 1999.
More than 57% of adults age 18 to 29
reported having had a sunburn.
Over 40% of children are reported to have
had sunburns over the preceding year.
How is it found?
 Mostly by self examination of the skin
 By observations by family members
 By skin examination during visits to the doctor
To catch it early, you have to LOOK for it!…
and then you have to DO something about it!
How is skin cancer treated?
The physician will:
 Determine what type it is (medical history,
examination, biopsy)
 Determine how localized or extensive it is
 Then treat it….
 surgery (e.g., Moh’s, cryo, laser, curettage, grafts)
 chemotherapy
 radiation