Cell Cycle and Cancer

• Cells need to divide to replace damaged cells or cells at the end of their life span.
• Cells need to divide to reproduce asexually to make genetic identical copies.
• Cells need to divide to grow tissues and organs in young organisms.
• Chromosomes are fancily packed DNA.
• In prokaryotic cells, DNA is packaged into a single, circular chromosome.
• In eukaryotic cells, DNA is packaged into multiple chromosomes.
• Humans have 46 chromosomes.
• Prokaryotes undergo binary fission once reached a certain size.
• Binary Fission: type of division that only prokaryotic cells do.
• In prokaryotes, the DNA duplicates, then the cell membrane indents before the cell divides into two new cells.
• Eukaryotic cells have a more complex cell cycle than prokaryotic cells.
• G1 phase involves cell growth.
• S phase involves DNA replication.
• G2 phase involves preparation for mitosis.
• The cell division stage, or M phase, has mitosis and cytokinesis.
• Internal regulators respond to events inside the cell.
• Internal regulators let the cell cycle process only when certain steps have already happened.
• External regulators respond to events outside the cell.
• External regulators direct cells to speed or slow down the cell cycle.
• Growth Factors: wound healing and embryonic development.
• In 9 months, one cell becomes millions of cells.
• Cells grow quickly during birth & puberty.
• During wound healing, growth factors turn on at the end of the wound.
• Cells at the edge of an injury are stimulated to divide rapidly.
• As the injury heals, the rate of cell division slows as the body heals and repairs itself.
• Cyclins: proteins that regulate the cell cycle.
• Apoptosis removes extra cells during development and wound healing and maintain structure.
• Apoptosis is programmed cell death. It has an important role in structuring tissues during growth and development.
• During apoptosis, the cell undergoes a series of controlled steps for self-destruction.
• Genetic changes can cause cancer as they lead to abnormal growth resulting in masses of tissues called tumors.
• Proto-oncogene: signals a cell to grow & divide.
• Tumor Suppressor Genes: signals a cell to stop dividing.
• DNA Repair Genes: preserve & maintain genetic codes.
• There are two types of tumors.
• Benign tumors remain in one place.
• Malignant tumors are able to spread.
• Through metastasis, malignant tumor cells will break off, travel through the body, and form tumors in other regions.
• Cancer cells do not respond to normal regulatory signals.
• The cell cycle is disrupted due to uncontrolled cell growth. Cells grow and divide uncontrollably.
• Cancer results from a defect in genes that control cell growth & division.