Cell Cycle and Reproduction Quiz

Cell Cycle and Cell Reproduction

• Cell reproduction in prokaryotes occurs via binary fission: DNA is copied, and the cell splits into two.
• Most bacteria can divide quickly, often with multiple copies of their chromosomes already formed.
• Reproduction speed varies greatly. E. coli can reproduce in about 20 minutes, and other types in 16-18 minutes.

Cell Division in Eukaryotes

• The cell cycle is a series of events in eukaryotic cells that leads to cell division. The cycle includes mitosis and cytokinesis.
• The cell cycle has specific phases: G1 (growth), S (synthesis of DNA), G2 (growth), and mitosis (division of the nucleus).
• At the G1 checkpoint, the cell can enter a non-dividing state called G0.
• During S phase, the cell makes a copy of all of its DNA.
• During G2 phase, the cell stockpiles the energy (like ATP) and other components it needs to divide.

The Cell Cycle

• Mitosis and cytokinesis are both essential parts of the cell cycle for eukaryotic cell reproduction.

Cell Reproduction in Eukaryotes

• DNA is copied during the S phase before mitosis.
• Mitosis is nuclear division.
• Four stages of mitosis include: prophase & prometaphase, metaphase, anaphase, and telophase.
• Cytokinesis is the division of the cytoplasm and other components of the cell.
• The divisions result in two daughter cells. For example, the parent cell splits into two daughter cells

Prophase & Prometaphase

• Chromosomes condense.
• Centrioles move to opposite ends of the cell.
• Spindle fibers form from centrioles.
• Nuclear envelope disappears (prometaphase).

DNA Packaging

• DNA (2 meters/6 feet long) must be compact to fit in the nucleus.
• DNA is tightly wrapped around proteins called histones.
• The histones then group together to form structures.

Metaphase

• Microtubules from centrioles pull and align chromosomes in the middle of the cell.
• Chromosomes align along the center (metaphase plate) of the cell.
• Chromosomal movement occurs via motor proteins along microtubules.

Anaphase

• The centromere splits, and sister chromatids pull apart.
• Motor proteins move chromatids along microtubules, which disassemble as they shorten.

Telophase

• Nuclear membranes form around the DNA at each end of the cell, creating two nuclei.
• The cell prepares to divide its cytoplasm.

Cytokinesis

• The cell splits.
• A ring of protein forms around the equator of the cell.
• The ring contracts, splitting the cell into two separate cells.

Mitosis & Cytokinesis Animation & Video

• Consult the Canvas site for animations of mitosis and cytokinesis.

Mitosis & Cytokinesis Summary

• This summarises the stages of mitosis and cytokinesis visualised by different stages of the phases.

Cancer

• Cancer is uncontrolled cell division.
• Mutant cells divide continuously without stopping. They bypass the typical cell cycle checkpoints.
• Large masses (tumors) form from fast-growing cells; the initial tumor is called the primary tumor.
• Cancer cells can metastasize, spreading to other areas and forming secondary tumors.

Getting Cancer

• Cancer is due to multiple genetic mutations causing uncontrolled cell growth.
• A multi-hit hypothesis suggests several mutations within the same cell are needed to develop cancer.
• Mutations that cause cancer include: mutations that signal the cell to divide when it shouldn't, mutations that deactivate apoptosis (programmed cell death), mutations altering contact inhibition, and mutations that affect the ECM for metastasis.

Factors that Can Increase the Risk for Cancer

• Environmental factors such as chemicals, radiation, and viruses can cause DNA mutations, increasing the risk of cancer.
• Genetics also play a role. Some people inherit a predisposition to cancer from their ancestors.

Treating Cancer

• Surgical excision can be used to remove primary tumors.
• Chemotherapy uses drugs that target rapidly dividing cells, including cancer cells, to halt cell division and growth.
• Radiation therapy uses ionizing radiation to damage cancer cells to kill cancer cells. This can also affect normal cells.
• Immunotherapy aims to boost the immune system to fight cancer cells.