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Questions and Answers
What is the primary role of cyclins in the cell cycle?
What is the primary role of cyclins in the cell cycle?
What type of errors can occur during mitosis?
What type of errors can occur during mitosis?
What is the effect of CDKs being activated at the wrong phase of the cell cycle?
What is the effect of CDKs being activated at the wrong phase of the cell cycle?
Which phase of the cell cycle does mitosis directly follow?
Which phase of the cell cycle does mitosis directly follow?
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What discovery did Walther Flemming contribute to the understanding of cell division?
What discovery did Walther Flemming contribute to the understanding of cell division?
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What is the role of cyclins in the cell cycle regulation?
What is the role of cyclins in the cell cycle regulation?
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What happens to cyclin concentration during the cell cycle?
What happens to cyclin concentration during the cell cycle?
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What is a consequence of kinetochores not being attached to spindle microtubules?
What is a consequence of kinetochores not being attached to spindle microtubules?
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Which of the following best describes the function of growth factors in the cell cycle?
Which of the following best describes the function of growth factors in the cell cycle?
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What occurs to cyclin levels at the G2 checkpoint?
What occurs to cyclin levels at the G2 checkpoint?
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What role do cyclins play in the cell cycle?
What role do cyclins play in the cell cycle?
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What occurrence is triggered by the maturation-promoting factor (MPF)?
What occurrence is triggered by the maturation-promoting factor (MPF)?
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How does the activity of cyclin-dependent kinases (Cdks) vary throughout the cell cycle?
How does the activity of cyclin-dependent kinases (Cdks) vary throughout the cell cycle?
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Which of the following statements about cyclins and Cdks is false?
Which of the following statements about cyclins and Cdks is false?
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What would likely happen if cyclin levels did not fluctuate during the cell cycle?
What would likely happen if cyclin levels did not fluctuate during the cell cycle?
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Study Notes
Cell Cycle Overview
- Living things reproduce by producing more of their own kind.
- The continuity of life depends on the reproduction of cells, or cell division.
Cell Division in Unicellular and Multicellular Organisms
- In unicellular organisms, cell division is the process of reproduction.
- Multicellular organisms use cell division for development (from a fertilized cell), growth, and repair.
Cell Division and Reproduction, Growth and Development, Tissue Renewal
- Cell division is a fundamental aspect of the cell cycle, from the cell's formation to its division.
- Each image illustrates a different aspect of cell division’s function: reproduction, growth and development, and tissue renewal.
Concept 12.1: Genetically Identical Daughter Cells
- Cell division typically creates genetically identical daughter cells with the same DNA.
- Meiosis is an exception; it produces gametes (sperm and egg cells) with half the number of chromosomes.
Cellular Organization of the Genetic Material
- A cell's genome comprises all the DNA within it.
- In prokaryotes, the genome is a single DNA molecule.
- Eukaryotic genomes consist of multiple DNA molecules.
- DNA is packaged into chromosomes within cells.
Eukaryotic Chromosomes
- Eukaryotic chromosomes are composed of chromatin—a complex of DNA and protein that condenses during cell division.
- Every eukaryotic species has a specific number of chromosomes per cell nucleus.
- Somatic cells (non-reproductive cells) have two sets of chromosomes.
- Gametes (reproductive cells) have half as many chromosomes as somatic cells.
Distribution of Chromosomes During Eukaryotic Cell Division
- Before cell division, DNA replicates, and chromosomes condense.
- Each duplicated chromosome has two sister chromatids—joined copies of the original chromosome.
- Sister chromatids are separated during cell division.
- The centromere is the narrow "waist" of a duplicated chromosome, where the sister chromatids are most closely attached.
Phases of the Cell Cycle
- The cell cycle consists of the mitotic (M) phase and interphase.
- Mitotic phase includes mitosis and cytokinesis.
- Interphase is where cells grow and copy chromosomes in preparation for cell division.
- Interphase is further broken down into G₁, S, and G₂ phases, where the cell grows during all three, but DNA replicates only during S phase.
Mitosis Phases
- Mitosis is conventionally divided into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.
- Cytokinesis overlaps the later stages of mitosis.
The Mitotic Spindle: A Closer Look
- The mitotic spindle is a structure composed of microtubules that controls chromosome movements during mitosis.
- In animal cells, the spindle microtubule assembly begins in the centrosome, an organizing center.
- The centrosome replicates during interphase, forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase.
- An aster, composed of short microtubules, extends from each centrosome.
- The mitotic spindle consists of centrosomes, spindle microtubules, and asters.
Kinetochores and Metaphase
- During prometaphase, some spindle microtubules attach to kinetochores of chromosomes, causing chromosome movement.
- Kinetochores are protein complexes at centromeres.
- At metaphase, chromosomes align at the metaphase plate, an imaginary plane midway between spindle poles.
- Sister chromatids separate and move toward opposite poles during anaphase, powered by depolymerization of kinetochore microtubules.
Nonkinetochore Microtubules and Cytokinesis
- Nonkinetochore microtubules from opposite spindle poles overlap and push against each other, causing cell elongation.
- Cytokinesis begins during anaphase (or telophase) and the spindle disassembles.
Cytokinesis: A Closer Look
- In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow.
- In plant cells, a cell plate forms during cytokinesis.
Loss of Cell Cycle Controls in Cancer Cells
- Cancer cells do not respond normally to the body´s control mechanisms.
- Cancer cells may not need growth factors.
- They may make their own growth factors, send signals without the factor, or have abnormal cell cycle control systems.
Transformation and Tumors
- Transformation is the process where a normal cell is converted into a cancerous cell.
- Tumors form from abnormal cells.
- Benign tumors remain localized.
- Malignant tumors invade surrounding tissues and may metastasize (spread to other parts of the body).
Recent Advances in Cancer Treatment
- Advances in understanding cell cycle and cell cycle signaling have led to improvements in cancer treatment.
Binary Fission in Bacteria
- Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission.
- During binary fission, the chromosome replicates, and the two daughter chromosomes move to opposite ends of the cell.
- The plasma membrane pinches inward, dividing the cell into two.
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Description
Test your knowledge on the role of cyclins and cyclin-dependent kinases (Cdks) in the cell cycle. This quiz covers mitosis, growth factors, and the consequences of errors during cell division. Dive into key discoveries and the regulatory mechanisms controlling the cell cycle phases.
