Biology 5.4 Cell Cycle Quiz

The Cell Cycle

• The primary function of the cell cycle is to produce new cells for growth, repair, and reproduction.
• The G1 phase of the cell cycle is characterized by cell growth and organelle production.
• DNA replication occurs during the S phase of the cell cycle.
• A cell typically spends approximately 90% of its life cycle in interphase.
• The major difference in cell division between prokaryotic and eukaryotic organisms is that prokaryotes divide by binary fission, while eukaryotes divide by mitosis and meiosis.
• The S phase follows the G1 phase in the eukaryotic cell cycle.
• From the end of the S phase until chromosomes are separated, the cell prepares for mitosis.
• The main purpose of cell division in multicellular organisms is to replace damaged cells, grow tissues, and produce reproductive cells.
• The contractile ring, formed by actin and myosin filaments, initiates the formation of the cleavage furrow during cytokinesis in animal cells.
• The contractile ring, composed of actin and myosin filaments, is primarily responsible for the contraction during cytokinesis.
• Cell cycle checkpoints are primarily responsible for regulating the progression of the cell cycle, preventing errors and promoting cell cycle completion when appropriate.
• During the G1/S checkpoint, the cell determines if conditions are favorable for DNA replication.
• If DNA replication is incomplete, entry into mitosis is blocked.
• Cyclins play a crucial role in regulating the cell cycle by activating cyclin-dependent kinases (CDKs), which control the progression of the cell cycle.
• Dysregulation of the cell cycle control system can lead to developmental abnormalities, diseases like cancer, and premature aging.
• A cleavage furrow, a groove that forms on the cell surface, is created during cytokinesis in animal cells.
• M cyclins are involved in regulating the progression of mitosis, ensuring the correct order of events.
• Cyclin-CDK complexes are activated and deactivated at each cell cycle stage, driving the progression through the different phases.
• The G1/S checkpoint is considered particularly crucial because it ensures that DNA is undamaged before replication.
• CDKs become active when they bind to cyclins.
• G1 cyclins are involved prior to DNA replication.
• Apoptosis is a programmed cell death characterized by a series of organized events, resulting in the cell breaking down into small membrane-bound fragments, while necrosis is uncontrolled cell death caused by external factors, leading to cell lysis.
• Caspases, a family of enzymes, are triggered by specific signals during apoptosis, initiating the cascade of events leading to cell death.
• The regulation of cell death is important in multicellular organisms for maintaining tissue homeostasis, preventing the accumulation of damaged cells, and regulating development.
• Apoptotic bodies are small, membrane-bound fragments formed from cells undergoing apoptosis.
• Density-dependent inhibition refers to the phenomenon where cells stop dividing when they come into contact with each other.
• The cell cycle becomes arrested when the G1 checkpoint detects damaged DNA.
• Cancer cells are characterized by uncontrolled cell division, a lack of density-dependent inhibition, and the ability to ignore the G1 checkpoint.
• Macrophages engulf and remove apoptotic bodies, preventing inflammation and promoting tissue repair.
• Telomeres, repetitive DNA sequences at the ends of chromosomes, protect against the loss of genetic information during DNA replication.
• Dysregulation of the cell cycle, leading to cancer, can be caused by mutations in genes that control cell growth and division, environmental factors, and lifestyle choices.
• Most healthy cells exhibit contact inhibition, stopping cell division when they come into contact with other cells.
• Telomere shortening, due to repeated DNA replication, triggers cell senescence.
• Telomerase, an enzyme, is responsible for adding new telomeric DNA repeats to chromosome ends.
• Cancer cells typically have telomerase activity, allowing them to maintain telomere length and continue dividing.
• The wild-type version of an oncogene is called a proto-oncogene.
• Telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, responsible for adding DNA repeats to telomeres.
• Oncogene mutations, loss of tumor suppressor genes, and telomere dysregulation can lead to unregulated cell growth and cancer.
• Induced mutations, caused by environmental factors like radiation, chemicals, or viruses, can lead to cancer.
• The TTAGGG sequence is repeatedly added to telomeres during extension.

The Cell Cycle

• The cell cycle is the series of events that take place in a cell leading to its division and duplication of its DNA and chromosomes.
• The cell cycle is divided into two major phases: interphase and the mitotic (M) phase.
• Interphase makes up approximately 90% of the cell cycle.
• Interphase is further divided into three phases: G1 phase (first gap phase), S phase (synthesis), and G2 phase (second gap phase).
• G1 phase: The cell grows, produces proteins, and assembles new organelles.
• S phase: DNA replication occurs.
• G2 phase: The cell prepares for mitosis, producing proteins necessary for cell division.

Mitosis

• Mitosis is the process of nuclear division, where one nucleus divides to form two identical daughter nuclei.
• Mitosis is divided into four stages: Prophase, Metaphase, Anaphase, and Telophase.
• Prophase: The chromosomes condense, the nuclear envelope breaks down and mitotic spindle fibers are formed.
• Metaphase: Chromosomes line up at the metaphase plate, attaching to spindle fibers.
• Anaphase: Sister chromatids separate and are pulled to opposite poles of the cell.
• Telophase: Daughter nuclei form and chromosomes become less condensed.
• Cytokinesis is the division of the cytoplasm, splitting the parent cell into two daughter cells. In animal cells, cytokinesis is characterized by the formation of a cleavage furrow. In plant cells, a cell plate is formed.

Cell Cycle Control

• Cell cycle checkpoints ensure proper execution of cycle events and prevent errors that could lead to cell death or cancer.
• Key checkpoints occur at the G1/S, G2/M, and M phases.
• Cell cycle progression is regulated by proteins called cyclins and cyclin-dependent kinases (CDKs).
• G1/S cyclins: Commit the cell to DNA replication.
• S cyclins: Required for DNA replication.
• M cyclins: Promote the events of mitosis.
• Apoptosis (programmed cell death) is a regulated process of cell elimination.
• Caspases are proteolytic enzymes that mediate apoptosis.
• Telomeres are protective caps at the ends of chromosomes that shorten with each cell division.
• Telomerase is an enzyme that replenishes telomeres, allowing cells to divide indefinitely.
• Cancer cells often have an increased expression of telomerase, contributing to their unchecked growth.

Mutations and Cancer

• Mutations in genes that regulate cell growth and division can lead to cancer.
• Oncogenes are mutated genes that promote uncontrolled cell growth.
• Proto-oncogenes are the normal versions of oncogenes and regulate cell growth.
• Mutations in proto-oncogenes can turn them into oncogenes.
• Mutagens, such as tobacco products, radiation, and certain viruses, can cause mutations.

Test your knowledge on the cell cycle and its phases with this quiz. Understand key concepts such as DNA replication, cell division differences, and the purpose of cell checkpoints. This quiz is perfect for biology students looking to reinforce their understanding of cellular processes.