Chapter Twelve Reading Journal

Questions:

What is the difference between mitosis and the cell cycle?
Mitosis includes prophase, prometaphase, metaphase, anaphase, and telophase this only makes up about 10% of the cell cycle the rest of the cell cycle is interphase that consists of G1, G2, and S phases. Mitosis is when the cell is actually in the process of dividing the other part of the cycle involves growth and DNA synthesis, which is most of the cells life. Although often the cells are in Go phase when they are told not to divide by the G1 checkpoint.

How do cells control the cell cycle?
Different cells divide at different rates and certain cells once in maturity never divide examples of these cells are muscle and nerve cells. The cell cycle has checkpoint after each of the sub phases of interphase and after mitosis. The checkpoint after G1 is called the restriction point and if it doesn’t receive the go ahead at this checkpoint it is sent into the non-dividing state called Go. Besides the checkpoints there are other molecules that regulate cell division mainly protein kinases and cyclin. Cyclin is constantly present but usually in the inactive form its active form is in higher concentration during S and G2 phases but is much lower during mitosis. Cells also regulate their cell cycles by knowledge of external factors such as surrounding density and anchorage.

What is known about how cancer cells differ from healthy cells?
Cancer cells don’t have good regulation of their cell cycles so they divide far too often. The fact that they are not anchorage dependant means that they can move from different parts of the organism and start growing in other places. The fact that they lack density dependency is the reason tumors form because the cells just layer on top of each other without stopping. They most also lack the cellular control of aptopsis or else they would self destruct because of their dysfunction.

Facts:
- Somatic cells contain 46 chromosomes gametes (reproductive cells) have 23 chromosomes
- Chromosomes are copied to from 2 sister chromatids which are attached at the centromere
- The five main phases of mitosis are prophase prometaphase metaphase anaphase and telophase the DNA needed for this division is produced during the S phase of interphase
- Microtubules play a major role in cell division because they attach to kinetochores and then shorten to separate the chromosomes that aligned in the middle during metaphase
- A benign tumor are cancer cells that stay in the place they started growing malignant tumors inhibit the function of major organs



This figure breaks down the various steps of mitosis. Doesn’t need much explaining I’m putting it on here because it explains.

Summary:
Cells are made up of genetic information that is packaged into chromosomes that are duplicated and then separated during cell division. The chromosomes duplicate to chromatids that are held together by the centromere. During interphase the cell grows and replicates DNA. It reaches several checkpoints before continuing and responds to many outside regulators. Cancer is somehow deficient in its regulation so its cell cycle malfunctions.