GEN BIO 1 | Mitosis and Cancer Cells

Mitosis

• produces two diploid (2n) somatic ells that are genetically identical to each other

• In humans, it ensures that every body cell has 23 pairs of chromosomes and occurs in growth and repair

diploid

cell with paired chromosomes from each parent

Order of Mitosis

1. Prophase

2. Prometaphase

3. Metaphase

4. Anaphase

5. Telophase

G2 Late Interphase

The nuclear envelope encloses the nucleus as the nucleolus is visible. Chromosomes cannot be seen individually.

Prophase

Chromosomes condense and become visible as nucleolus disappears. Spindle forms as centrosomes move to opposite poles.

Prometaphase

Nuclear envelope breaks up as the microtubules extending from each centrosome can now invade the nuclear area. Spindle fibers attach to kinetochores on chromosomes

Metaphase

Chromosomes line up along the center called the metaphase plate. Centrosomes are now at opposite poles of the cell.

Anaphase

Centromeres split as sister chromatids separate and move to opposite poles of the cell and the two ends should have the same complete collections of chromosomes.

Telophase

Nuclear envelope and nucleolus form at each pole, chromosomes decondense, nucleoli reappear and spindle disappears.

Cytokinesis

Division of cytoplasm into two cells

Animal Cytokinesis

Also known as cleavage, a ring of microfilaments contract and deepen the furrow

Plant Cytokinesis

Vesicles fuse at the middle forming a membranous disk called the cell plate, which grows outward until it reaches the cell wall.

Checkpoints

it ensures the cell does not enter one stage until previous stage is complete

G1 Checkpoint

Cell can undergo GO or apoptosis if DNA is damaged beyond repair; otherwise, it goes to the S phase.

G2 Checkpoint

Cell checks if DNA has been replicated properly.

M checkpoint

It makes sure the chromosomes are properly aligned and ready to partitioned to the daughter cells.

Apoptosis

The programmed cell death that shapes structures and kills potentially cancerous cells. It eliminates excess cells and weeds out aging or defective cells.

Apoptosis Process

1. Cell rounds up and nucleus collapses.

2. Chromatin condenses and DNA fragments.

3. Plasma membrane blisters and blebs form.

4. Cell and DNA fragments.

Development of Cancer Cells

1. Cell acquires a mutation for repeated cell division.

2. New mutations arise and one cell can start a tumor.

3. Cancer in situ. The tumor is at place or origin and one cell mutates further.

4. Cells have gained the ability to invade underlying tissue by producing a proteinase enzyme.

5. Cancer cells can invade the lymphatic and blood vessels

Benign Tumor

not cancerous, and does not grow larger due to being in a capsule of connective tissue

Malignant Tumor

cancerous and possesses ability to spread

Cancer Cell Characteristics

• look different from a normal cell

• are essentially immortal

• have uncontrolled division

• lack contact inhibition - cells usually stop dividing when they form a complete layer

• lack anchorage dependence - cells usually anchor to the dish surface and divide

Proto-oncogene

normal proteins stimulate cell division

Oncogene

mutated proto-oncogene; the abnormal proteins accelerate cell cycle

Tumor suppressor gene

normal proteins block cancer development

Mutated Tumor suppressor gene

abnormal proteins fail to block cancer development

Why does the nuclear envelope fragment?

It allows the spindle fibers to pull the chromosomes