Questions and Answers
What is the importance of cell division?
It is crucial in the process of heredity and variation, and allows cells to grow and reproduce.
What occurs during the S phase?
Active DNA synthesis (replication) occurs, resulting in the duplication of chromatin.
What happens during the G1 phase of the cell cycle?
The nucleus and cytoplasm enlarge, and the cell increases in volume by imbibing water and nutrients.
What is the M phase in the context of the cell cycle?
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In Coleus, the somatic cells are diploid with ___ chromosomes.
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How many kinetochores are present at prophase in Coleus?
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How many chromosomes are present at anaphase in Coleus?
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How many chromatids are present at metaphase I in Coleus?
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How many chromosomes are present at telophase after cytokinesis in Coleus?
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How many centromeres are present at anaphase in Coleus?
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How many chromosomes are present at telophase II after cytokinesis in Coleus?
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How many centromeres are present at anaphase I in Coleus?
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How many chromatids are present at metaphase in Coleus?
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Study Notes
Importance of Cell Division
- Essential for heredity and variation in all organisms.
- Takes place through a regular cycle, known as the cell cycle.
- Facilitates growth and reproduction of cells, ensuring metabolic activities are consistent.
Interphase (Non-Dividing Phase)
- Characterized by a distinct nucleus surrounded by a nuclear membrane.
- Contains nucleoli and chromatin, which appears as a granular network of darkly staining material.
Phases of the Cell Cycle
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G1 Phase:
- Cell growth occurs as the nucleus and cytoplasm enlarge.
- Volume increases through the absorption of water and nutrients.
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S Phase:
- Active DNA replication takes place, doubling the chromatin from 2c to 4c.
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G2 Phase:
- RNA and protein synthesis essential for chromosome formation are active.
- Chromatin fibers condense to form visible chromosomes.
Mitosis (M Phase)
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Occurs in somatic and germ cells, essential for cellular proliferation and tissue replacement.
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Involves four distinct stages:
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Prophase:
- Chromosomes shorten, thicken, and become visible as distinct rods.
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Metaphase:
- Chromosomes are maximally condensed and align at the equatorial plate.
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Anaphase:
- Centromeres split, and sister chromatids move to opposite poles.
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Telophase:
- Chromosomes regroup into two distinct nuclear regions.
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Relation to Heredity
- Mitosis maintains a constant chromosome number through successive divisions.
- Daughter cells have the same chromosome composition as parent cells, making it an equational division.
Meiosis
- Occurs during gametogenesis—spermatogenesis and oogenesis in animals, megasporogenesis in plants.
- Comprises two rounds of division: Meiosis I and Meiosis II.
Prophase I of Meiosis
- The first step in meiosis, pivotal for genetic variety in gametes.
Chromosome Structure in Coleus
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Somatic cells are diploid, containing 24 chromosomes.
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Key chromosome details at specific stages of mitosis and meiosis include:
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Kinetochores at Prophase: Present at the end of prophase.
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Chromosomes at Anaphase: Each sister chromatid is a separate chromosome.
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Chromatids at Metaphase I: Present as homologous chromosome pairs.
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Chromosomes at Telophase after Cytokinesis: Two distinct nuclei formed.
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Centromeres at Anaphase: Centromeres separate allowing chromatids to migrate.
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Chromosomes at Telophase II after Cytokinesis: Results in haploid cells.
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Centromeres at Anaphase I: Remain attached for each homologous chromosome.
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Chromatids at Metaphase: Sister chromatids align centrally.
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Description
Test your understanding of the cell cycle and the importance of cell division in heredity and variation. This quiz covers the interphase and the overall functioning of cells in all organisms. Get ready to explore the foundational concepts in genetics and cell biology!
