Questions and Answers
What does the term diploid (2n) refer to in animals?
Germ cells are haploid and carry two copies of each chromosome.
False
What is the primary purpose of the G1 stage in the cell cycle?
Cells create organelles for energy and protein production.
During interphase, individual chromosomes are in a less condensed form known as __________.
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Match the following stages of the cell cycle with their descriptions:
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What phase of the cell cycle is collectively known as interphase?
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The cell spends about 90% of its time in interphase during the cell cycle.
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What happens to cells in the G0 stage?
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Passage from G1 to S stage in the cell cycle is governed by a __________.
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What is the main consequence of derangements of the cell cycle?
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What is the primary role of p53 in the cell cycle?
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Sister chromatids are formed during the G1 phase of the cell cycle.
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What happens during the G2 stage of the cell cycle?
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The process of __________ involves the separation of sister chromatids.
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Match the cell cycle phase with its main event:
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Which of the following statements about mitosis is correct?
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Cancer cells often complete the cell cycle without proper DNA integrity checks.
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What is the significance of the centromere?
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The accumulation of mutations in cells can lead to the formation of __________.
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Which of the following best describes oncogenes?
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What happens to the nuclear membrane during prophase?
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Centrosomes contain two tubulin-based centrioles.
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What occurs during anaphase?
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During ______, the chromosomes align at the equatorial plate.
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Match the following stages of cell division with their descriptions:
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What is the role of kinetochores in mitosis?
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Cytokinesis occurs before telophase.
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How many divisions can human somatic cells typically undergo?
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The ______ disappears during telophase.
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What marks the end of telophase?
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Study Notes
Cell Composition and Phases
- Autosomal cells are diploid (2n), containing two copies of each chromosome, while germ cells are haploid (n) with one copy.
- In humans, autosomal (46 chromosomes) and germ cells (23 chromosomes) reflect inheritance from both parents.
- Eukaryotic cells undergo replication in a defined cell cycle, leading to cell growth, DNA synthesis, and division.
The Cell Cycle Overview
- The cell cycle has four phases: G1 (presynthetic gap), S (synthesis), G2 (postsynthetic gap), and M (mitosis).
- Interphase (G1, S, G2) comprises 90% of the cell cycle duration; actively dividing cells spend most time here.
- Cells in the G0 phase are metabolically active but not preparing to divide.
Interphase Details
- Chromosomes are in chromatin form during interphase, allowing access for transcription.
- Mitosis requires the DNA to condense into chromosomes for distribution during division.
G1 Stage: Presynthetic Gap
- Organelles for energy (mitochondria) and protein production (ribosomes, endoplasmic reticulum) are synthesized.
- A restriction point ensures criteria, like DNA integrity, are met before transitioning to S phase.
S Stage: Synthesis of DNA
- Genetic material replication occurs, resulting in two identical sister chromatids per chromosome.
- The cell remains diploid (46 chromosomes) despite duplication of chromatids (92).
G2 Stage: Postsynthetic Gap
- Another quality control checkpoint checks for sufficient organelles and correct DNA replication.
- Ensures preparedness for mitosis.
M Stage: Mitosis and Cytokinesis
- Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase, concluding with cytokinesis.
- Results in two genetically identical daughter cells in autosomal cells.
Cell Cycle Control and Cancer
- Checkpoints are critical for preventing division of damaged or inadequately sized cells; key checkpoints are G1/S and G2/M.
- p53 protein plays a vital role in DNA damage response and checkpoint function.
- Cyclins and cyclin-dependent kinases (CDKs) drive cell cycle progression, forming complexes to activate transcription factors.
Cancer Characteristics
- Mutations in genes like TP53 (coding for p53) lead to uncontrolled cell division, contributing to cancer development.
- Cancer cells may exhibit rapid division and metastasis through bloodstream or lymphatic systems.
Mitosis Phases
- Prophase: Chromatin condenses, nuclear membrane dissolves, centrioles migrate and form spindle fibers.
- Metaphase: Chromosomes align at the metaphase plate, attached by kinetochore fibers.
- Anaphase: Separation of sister chromatids as they are pulled toward opposite poles.
- Telophase: Nuclear membranes reform, chromosomes uncoil, and nucleoli reappear; followed by cytokinesis, separating cytoplasm.
Limit on Cell Divisions
- Human somatic cells divide roughly 20 to 50 times before undergoing programmed cell death, limiting continuous division.
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Description
Explore the differences between diploid and haploid cells in this quiz focusing on the cell cycle in eukaryotic organisms. Understand how these concepts are essential for human genetics and the implications of cell cycle derangement. Test your knowledge with questions designed to enhance your grasp of this fundamental biological topic.
