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Chapter 10- Cell Cycle & Cellular reproduction - Coggle Diagram
Chapter 10- Cell Cycle & Cellular reproduction
Parts of a chromosome
Duplicated chromosomes
- composed of
sister chromatids
joined at the centromere
each sister chromatids has
identical
DNA
chromosomes start as "I" formation with one chromatid
then, to duplicate DNA, chromosomes must go through
DNA replication
turns into "X" formation
this is to get ready for cell division
Karyotype
- a pictorial display of chromosomes arranged by morphology
all cells exist in diploid form. all exist in 2 copies (2 chromosomes of each kind)
only eggs and sperm are haploid (half of that)
DNA is organized in prep for
Cellular Replication
every human cell contains about
2 meters
of DNA
nucleus is only ~6um in diameter
- chromosomes are 50% protein
Histone Proteins
package the DNA
highly conserved
provide structure for DNA to get wrapped around
gets folded and coiled many times to reach final chromosome form
DNA is packaged into
chromatin
which becomes condensed for mitosis
Uncondensed DNA (
euchromatin)
active chromatin- genes are being transcribed into mRNA
non-dividing
DNA condensed into chromosomes (
heterochromatin)
genes are inaccessible for transcription
dividing
Cell Division
Cells divide to
generate new cells
for regular cell turnover
(ex. skin turns over every 10-30 days)
Cells divide to help in
wound healing
Cells divide to allow
growth & development
^ ESSENTIAL FOR LIFE!
not all cells divide regularly!
Before a cell can divide:
Cell must duplicate its DNA
Cell must separate the DNA, cytoplasm, & organelles
HOW CELLS REPLICATE
The Cell Cycle
interphase
most of cell cycle is spend here (20 hrs)
normal functions happening
G1
- cell grows in size. double organelles
S
- synthesis (DNA replication occurs / results in sister chromatids)
G2
- finally prep for cell divison
Checkpoints
allow the cell to fix problems before continuing on in the cell
controlled by proteins called
cyclins
ex p53 stops cycle at G1 when DNA is damaged and initiates DNA repair
cells that are damaged undergo
apoptosis
programmed cell death
cells round up, lose contact with neighbors and the nucleus fragments
engulfed by white blood cells
**balance** between cell division and apoptosis
if this does not occur = damaged cells could be replicated = cancer and/or other problems
Mitosis
division of the nucleus
Prophase
Prometaphase
metaphase
Anaphase
Telophase
Mitosis
Prophase
(step one)
chromatin condenses and chromosomes become visible
parental chromo. already duplicated are are sister chromatids
nucleolus disappears and nuclear envelope fragments
spindle fibers
start to assemble and two centrosomes migrate away from each other
Asters
brace the centrioles
Prometaphase
(late prophase)
Kinetochores
appear on each side of the centromere and attach sister chromatids to the kinetochore spindle fibers
Spindle Fibers
extend from the poles to the chromosomes
chromo. are not yet aligned
Metaphase
(Chromo. align at midline)
centromeres are now alignment on a single plane at center of the cell -->
Metaphase plate
Polar spindle fibers
reach beyond the metaphase plate and overlap
M CHECKPOINT
holds the cell here till kinetochores are attached property to the spindle fibers and chromosomes are aligned properly.
Anaphase
(separation of sister chromatids)
two sister chromatids separate at the centromere
daughter chromosomes
each have a centromere and a single chromatid
daughter chro. move to opposite poles
(shortest phase)
Telophase
(formation of daughter cells)
Spindle fibers disappear as new nuclear envelopes form around daughter chromatids
each nucleus contains same # / kinds of chromosomes
chromos. become more diffuse again (less condensed) and nucleolus reappears
Cytokinesis
(division of daughter cells)
Division of the cytoplasm
formation of a
cleavage furrow
indentation
contractile ring of actin filaments cinches the cell
Why is exact replication so important?
mutations can lead to
cancer
cancer
is uncontrolled cell division
Benign
- not cancerous
Malignant
- cancerous with the ability to spread
Characteristics of cancer cells
cancer cell lacks
differentiation
(look abnormal)
Have abnormal nuclei (enlarged etc)
DO NOT UNDERGO APOPTOSIS
form tumors through the loss of
contact inhibition
undergo
metastasis
and
angiogenesis
(become invasive + grow blood vessels)
cancer originates usually through multiple mutations to genes affecting the balance between signals that promote the cell cycle and signals that inhibit it
What causes mutations?
Genetics
environmental factors:
radiation
environmental carcinogens (tobacco and pollutants)
viruses
Mutations -->
Proto-oncogenes
(triggers mitosis)
Proto-oncogenes --->
Oncogenes
(promotes cells division)
- proto-oncogene
= gas pedal for mitosis (when working normally)
when proto are not working correctly
like a brick on the gas pedal. (way to much mitosis)
Tumor suppressor genes
- normally keep cells from dividing uncontrollably