Cell cycle/mitosis

What is the "cell cycle?"

A repeating sequence of cellular events that includes interphase, mitosis, and cytokinesis.

Why would we say that cancer (malignant) cells are essentially immortal?

Because cancer cells continue to grow no matter what. There is nothing within the body that can stop their growth.

Are cells from older persons different from cells from younger persons in relation to the number of divisions they will pass through before dying out?

Cellular senescence has been attributed to the shortening of telomeres with each cell cycle; when telomeres become too short, the cells die. Obviously, the older you get, the faster your cells will die.

It has been shown that mice that are put on a reduced calorie diet live longer than mice that are fed more highly caloric diets. How does this relate to ideas about aging?

Clearly, reducing calorie intake slows the aging process, or higher calorie diets increase the aging process.

Cells that are not malignant will only go through a limited number of divisions before they die out. How many cell cycles will normal cells go through? How has this been related to "Intrinsic" ideas about aging?

Depends on the type of cell; the number of cell cycles vary based on this. They go through them until they stop being able to pass checkpoints. Intrinsic aging is influenced by internal physiological factors alone.

What event usually makes cells in a population of cells stop going through the cell cycle?

If a cell doesn't get past a "checkpoint" then that cell will stay at its current phase until it dies (at g0 phase if it cannot grow). If there is a genetic mutation (at g2), the cell dies. Mitosis and cytokinesis makes up the M phase.

Cells reproduce in a process called mitosis producing "exact" genetic copies of themselves. Describe the cellular events of mitosis including what happens to plasma membrane, nuclear membrane, chromosomes, centrioles, spindle fibers.

Interphase is the limbo phase. Prophase; the nucleoli disappears and the chromatin (what makes up chromosomes; little threads) condenses into chromosomes. The nuclear envelope (protects nucleus), breaks down. The mitotic spindle is assembled. Metaphase; the chromosomes are distributed across the barrier that lies between the mitotic spindle. The mitotic spindle pulls the chromosomes apart creating chromotids (half the chromosome). Anaphase; separation of chromatids as far away as they can go (to poles/centrioles). Telephase; the nuclear envelope develops around each pole. Begins becoming separate cells (plasma membrane).

Name the phases of the cell cycle and briefly state what is happening during each. Which phase is the shortest?

Interphase; growth and DNA synthesis occur when the nucleus is not actively dividing. Mitosis is a type of cell division in which daughter cells receive the exact chromosonal and genetic makeup of the parent cell and this occurs during growth and repair. Cytokinesis is the division of the cytoplasm following mitosis and meiosis. Cytokinesis is the shortest phase.

Name three ways that cell division by mitosis is important for an organism such as yourself.

It is a vital process in the growth and development of our bodies and of other living creatures. Mitosis also helps the cells to divide and replace the worn out cells. It also plays important role in healing and repair etc.

In a cell with 46 chromosomes, what is the number and condition of the chromosomes in each phase of mitosis - prophase, metaphase, anaphase, and telophase?

Prophase has 46 chromosomes. Metaphase has 46, and they're lined up along the horizontal axis between the centrioles. Anaphase has 23 chromosomes being separated by the spindle fibers (chromatid). Telophase has 23 and is continued being separated.

What do "extrinsic" ideas about aging attribute the aging process to?

The 'real hazards of mortality' are, in typical circumstances, predation, disease, and accidents.

Scientists have bred populations of fruit flies that live significantly longer than other fruit fly populations. Would this support and intrinsic or extrinsic view of aging?

This would support the intristic view of aging, as the fruit flies are being bred, which involve internal factors. They are not being exposed to certain conditions, which would make it extrinsic.

Sometimes cells continue cycling at a time and place when they should stop and differentiate into specialized cells. What happens when cells do this?

When cells continue to grow after reaching a certain point, they turn into cancer cells (void checkpoints in body).