Cell Cycle, Cancer Cells, Differentiation, & Stem Cells

Why do cells divide?

Cells divide when their SA/V ratio decreases. They divide to slow the process of getting nutrients and removing waste products from the entire internal volume.

What is the purpose of each type of division?

The purpose of division is growth (mitosis), repair/healing (mitosis), cellular replacement of the stomach lining and outer layer of skin, and reproduction (meiosis).

What are the two main phases of the cell cycle?

The mitotic phase and interphase.

What two processes occur during the M phase?

Mitosis and cytokinesis.

What are the three stages of interphase?

G1, S, and G2.

List some examples of what cells are doing during interphase.

Cells increase in size, make protein, repair, transport substances, move, and perform their normal metabolic functions, such as cellular respiration or photosynthesis.

What happens during S phase?

DNA replicates. A cell synthesizes a new set of DNA.

Why does DNA replicate?

To ensure that every cell receives a complete set of DNA.

Describe the two forms of DNA, including when they appear during the cell cycle.

DNA appears as chromatin in interphase and as chromosomes in cell division. Each chromatin strand is an extremely long double helix of DNA that is unraveled. A chromosome is the opposite, each one made up of two identical DNA strands, or sister chromatids.

What is a centromere?

A centromere holds together the two strands of DNA once they replicate.

What are sister chromatids?

Replicated strands of DNA are called sister chromatids.

What occurs in late G2 in preparation for mitosis?

Two centrosomes appeared outside the nucleus. These organelles will direct mitosis.

What do microtubules do?

Microtubules extend from the centrosomes and will move chromosomes during mitosis.

What is G0?

Some cells that leave the cell cycle and stop dividing. This can be permanent, such as in brain cells, or temporary, such as in some stem cells.

Prophase

Nuclear membrane is broken down, chromatin condenses into chromosomes, centrosomes migrate to opposite poles of the cell, microtubules gather into larger structures called spindle fibers, spindle fibers attach to the centromere of chromosomes at a specialized protein called the kinetochore.

Metaphase

chromosomes migrate to the metaphase plate (middle).

Anaphase

Chromosomes are pulled apart, cytokinesis begins with the furrowing of the cell membrane.

Telophase

Essentially the opposite of prophase, nuclear membrane reforms, chromosomes unwind into chromatin, microtubules disappear, centrosomes migrate near the nucleus.

What is cytokinesis?

Cytoplasm divides into two cells.

How is cytokinesis different in plants and animals?

Animal cells form a furrow that divides the cytoplasm into two parts, while plant cells develop a cell plate that forms in the middle of the divided nuclei.

what are similarities among all niches?

all niches follow the same pattern to differentiate. signals are released to activate the stem cell. the stem cell divides. one becomes a specialized cell and the other stays in the niche. the signals activate genes that will transform the stem cell (the cell that is leaving will differentiate, different DNA gets activated for each niche)

what are some specific differences between all niches?

located in different places on your body, makes different kinds of cells, cells perform different functions, different genes transform the cells

how are embryonic stem cells different from adult stem cells?

embryonic stem cells have not become specialized and can become any type of cell. adult stem cells can differentiate into the specific type of cells they are surrounded by and can only become a few types of cells.

how could stem cells be used to cure medical conditions or diseases?

certain kinds of adult stem cells also might be able to develop into different kinds of cells, providing new treatments for many diseases and conditions (grow stem cells and manipulate them into the cells you need to replace)

cells divide, differentiate, or die. what is differentiation?

cells stop dividing to specialize in structure and function

what is apoptosis? what is its purpose?

cell death, a process that eliminates unnecessary cells during development and removes unhealthy/damaged cells in a mature organism

what are cell cycle regulators?

proteins that control the progression of a cell through the cell cycle, can either stimulate or inhibit cell cycle progression, instruct cells to differentiate, or initiate cell death

what happens if cell cycle regulators don't function properly?

an organism may end up with too few or too many cells, can cause problems of varying severity

criteria for G1 checkpoint?

no DNA damage, sufficient resources

criteria for S checkpoint?

no errors during DNA replication

criteria for G2 checkpoint?

DNA without damage, chromosome set complete, and enough cell components

criteria for M checkpoint?

all sister chromatids attached to mitotic spindle/spindle fibers

what are stimulating proteins encoded by?

proto-oncogenes

what are inhibitory proteins encoded by?

tumor suppressor genes

cancer is the result of an improperly regulated cell cycle. what are two reasons for why cells can form tumors?

too much cell division, too little cell death

normally, proto-oncogenes stimulate the cell cycle. what are oncogenes and how do they affect the cell cycle?

mutated versions of proto-oncogenes, increase stimulation, leads to uncontrolled cell division

normally, tumor suppressor genes inhibit the cell cycle. how do mutated tumor suppressor genes affect the cell cycle?

can cause a loss of inhibition, leads to uncontrolled cell division, fails to stop cell cycle