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Questions and Answers
What is the primary purpose of mitosis?
What is the primary purpose of mitosis?
During which phase of mitosis do sister chromatids separate?
During which phase of mitosis do sister chromatids separate?
What significant event happens during meiosis that is not part of mitosis?
What significant event happens during meiosis that is not part of mitosis?
What role do the spindle fibers play during mitosis?
What role do the spindle fibers play during mitosis?
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Which process leads to genetic variation among gametes?
Which process leads to genetic variation among gametes?
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What occurs during the telophase of mitosis?
What occurs during the telophase of mitosis?
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Which cell division process is responsible for asexual reproduction?
Which cell division process is responsible for asexual reproduction?
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Which statement best describes cytokinesis?
Which statement best describes cytokinesis?
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What is the name of the complex formed by DNA and proteins in the nucleus?
What is the name of the complex formed by DNA and proteins in the nucleus?
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What discovery did Walther Flemming make related to cell division?
What discovery did Walther Flemming make related to cell division?
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What role do histones play in relation to DNA?
What role do histones play in relation to DNA?
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During which phase of the cell cycle do chromosomes duplicate?
During which phase of the cell cycle do chromosomes duplicate?
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What is the purpose of the centromere in a chromosome?
What is the purpose of the centromere in a chromosome?
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Which of the following statements about genes is correct?
Which of the following statements about genes is correct?
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Which phase of the cell cycle is known as the resting phase?
Which phase of the cell cycle is known as the resting phase?
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What type of cell division results in haploid cells?
What type of cell division results in haploid cells?
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Study Notes
Structure of Chromosomes
- The nucleus contains most of the cell's DNA, organized into discrete units called chromosomes.
- Each chromosome contains one long DNA molecule associated with many proteins.
- This DNA and protein complex is called chromatin.
- When a cell is not dividing, chromatin appears as a long thread.
- When a cell is dividing, chromatin condenses to form chromosomes.
- Chromatin is a colored body (chroma) and a body (soma).
Chromatin
- Chromatin material forms a fibre made of two components:
- DNA, made of repeating nucleotides (phosphate, sugar, nitrogenous base).
- Nucleotides are joined by complementary nitrogenous bases: Adenine, Guanine, Cytosine, Thymine.
Histones
- Histones are proteins that help coil and package DNA into structural units called nucleosomes.
- Nucleosomes contain eight histone proteins.
Chromosome Structure
- A chromosome, in its condensed form during cell division, consists of two sister chromatids joined at the centromere.
- The centromere is the point of attachment for spindle fibres during cell division.
Genes
- Genes are specific sequences of nucleotides on a chromosome.
- They encode particular proteins, expressing specific features of the body.
- Genes are units of heredity passed from parents to offspring.
Cell Cycle
- The cell cycle describes a series of events leading to DNA duplication and cell division, producing two daughter cells.
- The cell cycle consists of two phases:
- Interphase (non-dividing phase):
- First growth phase (G1): Resting phase, no chromosome change.
- Synthesis phase (S): DNA synthesis and chromosome duplication.
- Second growth phase (G2): More RNA synthesis.
- M-phase (dividing phase):
- Mitosis and cytokinesis
- Interphase (non-dividing phase):
Mitosis
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Mitosis is a type of cell division where a parent cell divides into two identical daughter cells.
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Chromosome number remains the same after mitosis.
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Mitosis has four phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
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Mitosis is crucial for:
- Growth
- Repair
- Replacement
- Asexual reproduction
Meiosis
- Meiosis is the cell division that produces sex cells (gametes).
- Meiosis reduces the chromosome number to half (haploid).
- Meiosis is important for:
- Halving chromosome numbers
- Mixing up genes
Meiosis Phases
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Meiosis involves two divisions:
- Prophase I, Metaphase I, Anaphase I, Telophase I (First division)
- Prophase II, Metaphase II, Anaphase II, Telophase II (Second division)
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Crossing over and mixing of maternal and paternal chromosomes happen during meiosis.
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Description
This quiz covers the essential concepts related to the structure of chromosomes and chromatin within the cell nucleus. It explores the composition of DNA, histones, and the formation of nucleosomes, as well as the behavior of chromatin during cell division. Test your understanding of these fundamental biological structures.
