Mitosis

Cell division

What is the process by which a parent cell divides into two daughter cells?

Mitosis

➢ Division of the nucleus in SOMATIC CELLS

➢ Only occurs in eukaryotes

➢ Doesn't occur in some cells such as brain cells after maturity

G1 (growth), S (DNA synthesis), and G2 (growth and preparation for mitosis).

What are the three main phases of the cell cycle?

G1 phase

❖ G stands for gap; the first growth stage after cell division

❖ The cell synthesizes mRNA and proteins needed for

chromosome replication

❖ Cells mature by making more cytoplasm and organelles

S phase

Chromosomes are replicated; each chromosome

consists of 2 chromatids

Chromosomes

rod-shaped, filamentous bodies present in the nucleus

chromatin

- Not visible in the active nucleus due to their high-

water content

- Undergo folding, coiling, and supercoiling during cell division

chromatid

-chromosomes become progressively thicker and smaller and now are visible under light microscope

histones

proteins that support dna

G2 phase

- The cell grows

- All cell structures needed for division are made

- both organelles and protein are synthesized

Prophase, Metaphase, Anaphase, and Telophase (PMAT).

What are the four stages of mitosis?

euploidy

presence of a whole set of chromosomes

aneuploidy

missing chromosomes in a whole set which can cause defects

brain cells

What type of cells do not undergo mitosis after maturity?

Astral microtubules

microtubules with short grip

Polar Microtubule

- overlaps in the middle of the spindle and pushes the poles further

kinetochore microtubules

They direct chromosomes toward the metaphase plate during cell division.

PROPHASE

- chromosomes condense and are now visible using an ordinary microscope.

- centrioles move from opposite poles and produces spindle fibers

LATE PROPHASE

❖ Nuclear envelope and nucleolus disappear.

❖ Kinetochore, a special protein complex, appears at the centromere

Metaphase

Kinetochore microtubules directs the chromosomes toward the center of the cell in the are known as equatorial plate

Anaphase

❖ Kinetochore microtubules of the spindle fibers separate

and move the chromatids towards opposite poles

❖ Polar microtubules begin to elongate, while the astral

microtubules pull them on the other side

Telophase

❖ Chromosomes decondense going back to chromatin fibers

❖ Spindle fibers deconstructs and will become the future

cytoskeleton of the cell

❖ The nuclear envelope reappears

cleavage furrow

produced by the contractile ring, constricting the middle of the cell to divide the cytoplasm.

cytokinesis

❖ Physical process of cell division

❖ Cytoplasm divides into two daughter cells

checkpoints

- monitor cell division

G1/S PHASE CHECKPOINT

❖ checkpoint that Evaluates the DNA's integrity; prevents cells with

❖ Evaluates the cell's capability to undergo cell division

P53 PROTEIN (tumor-suppressing protein)

❖ monitor G1/S phase checkpoint

❖ Located in chromosome 17

❖ can trigger cell cycle arrest or apoptosis

❖ If this mutates, mitosis WOULD NOT stop which result in cancer.

▪ The cell will repair itself first

▪ Repair unsuccessful: Cells will remain permanent in G0

▪ Cell will udnergo apoptosis

P53 instuctions to chromosomes

G2/M phase checkpoint

❖ Checks activities in G2 to ensure its proper flow

❖ Ensures that DNA synthesis is complete before mitosis

SPINDLE ASSEMBLY CHECKPOINT (M-A)

❖ Guarantees the proper alignment of the chromosomes of

the metaphase plate

❖ Ensures that the number of the parent cell is equal to its

daughter cell

❖ Ensures the growth of the offspring

❖ Replaces the damaged cells in wound

IMPORTANCE OF MITOSIS

CANCER

➢ Occurrence of mutation and did not follow check point, these mutated cells

➢ Mitosis is not controlled = unlimited cell division

TUMORS

Mass of abnormal cells

Benign Tumor

o Abnormal cells remain at original site as a lump

o Do not cause serious problems

o Can be removed by surgery

malignant tumor

o Cells leave original site

▪ Lose attachment to nearby cells

▪ Carried by blood & lymph system to other tissues

▪ Start more tumors = metastasis

o Impair functions of organs throughout body

Angiogenesis

refers to the process where new blood vessels

grow from existing ones, supplying tumors with oxygen and

nutrients.

Radiation Therapy

o Uses beams of intense energy to kill cancer cells

o Uses X-Rays, but protons or other types of energy also can be used

Chemotherapy

o Powerful chemical to kill fast-growing cells

o Most often used

Cancer Surgery

o Operation: removes tumor and nearby tissues

o Oldest type

o Surgical Oncologist - treats cancer with surgery

Immunotherapy

o "biologic therapy"

o Boost the body's natural defense; using substances made by the body or lab to improve the immune system