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Questions and Answers
In which phase of mitosis do chromosomes align at the metaphase plate?
In which phase of mitosis do chromosomes align at the metaphase plate?
- Metaphase (correct)
- Anaphase
- Prophase
- Telophase
Cytokinesis refers to the process of nuclear division.
Cytokinesis refers to the process of nuclear division.
False (B)
What is the primary result of meiosis?
What is the primary result of meiosis?
four daughter cells
During ____ phase, spindle fibers pull apart the chromatids towards opposite poles of the cell.
During ____ phase, spindle fibers pull apart the chromatids towards opposite poles of the cell.
Match the following processes or phases with their descriptions:
Match the following processes or phases with their descriptions:
How many pairs of chromosomes are found in the human body?
How many pairs of chromosomes are found in the human body?
The S-phase of interphase is responsible for DNA replication.
The S-phase of interphase is responsible for DNA replication.
What are the two major phases of the cell cycle?
What are the two major phases of the cell cycle?
The cell spends approximately _______ hours in interphase.
The cell spends approximately _______ hours in interphase.
What is the purpose of the G2 phase in interphase?
What is the purpose of the G2 phase in interphase?
Match the stages of mitosis with their key events:
Match the stages of mitosis with their key events:
Cytokinesis is the division of the nucleus during cell division.
Cytokinesis is the division of the nucleus during cell division.
What type of cells undergo mitosis?
What type of cells undergo mitosis?
What does DNA stand for?
What does DNA stand for?
Mitosis and meiosis are the same processes of cell division.
Mitosis and meiosis are the same processes of cell division.
What are genes recognized as?
What are genes recognized as?
DNA consists of two strands that wind around each other to form a double ______.
DNA consists of two strands that wind around each other to form a double ______.
What is the structural role of histones in chromosomes?
What is the structural role of histones in chromosomes?
Telomeres are made of coding DNA sequences.
Telomeres are made of coding DNA sequences.
The term 'chromosome' comes from the Greek words 'khroma' meaning color and 'soma' meaning ______.
The term 'chromosome' comes from the Greek words 'khroma' meaning color and 'soma' meaning ______.
Match the terms with their definitions:
Match the terms with their definitions:
What process does meiosis I include that allows for genetic diversity?
What process does meiosis I include that allows for genetic diversity?
During Telophase II, the chromosomes de-condense back into chromatin.
During Telophase II, the chromosomes de-condense back into chromatin.
What happens during Anaphase I?
What happens during Anaphase I?
The stage between Meiosis I and Meiosis II that does not involve DNA replication is called __________.
The stage between Meiosis I and Meiosis II that does not involve DNA replication is called __________.
Match the stage of meiosis with its description:
Match the stage of meiosis with its description:
In which stage of meiosis do spindle fibers attach to the centromeres of chromosomes?
In which stage of meiosis do spindle fibers attach to the centromeres of chromosomes?
Meiosis II is essentially the same process as mitosis but occurs in haploid cells.
Meiosis II is essentially the same process as mitosis but occurs in haploid cells.
During __________, centrosomes duplicate and start producing spindle fibers in both meiosis I and II.
During __________, centrosomes duplicate and start producing spindle fibers in both meiosis I and II.
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Study Notes
Molecular Biology: Lesson 3 Study Notes
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Connection between DNA, Genes, and Chromosomes
- Genes are the basic units of heredity, sequences of nucleotides in DNA or RNA encoding for RNA or protein synthesis.
- DNA (deoxyribonucleic acid) carries hereditary materials and genetic instructions, organized into a double helix structure made of nucleotides.
- Chromosomes are condensed DNA structures that contain genetic material, coiled around histones for structural support; humans have 46 chromosomes (23 pairs).
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Telomeres
- Telomeres protect chromosome ends with repetitive non-coding DNA sequences.
- They shorten with each cell division, ultimately limiting further divisions once they become critically short.
Cell Cycle Overview
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Definition and Phases
- The cell cycle is a series of ordered events leading to cell growth and division into two daughter cells.
- Comprises two main phases: Interphase and M-phase (mitosis).
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Interphase
- Longest stage (approximately 24 hours); accounts for about 90% of a cell's life.
- Stages of Interphase:
- G1 Phase: Growth phase where structural proteins and enzymes are synthesized; cellular contents duplicated (excluding chromosomes).
- S-phase: DNA replication occurs, doubling genetic material before division.
- G2 Phase: Cell prepares for division, replenishing energy and duplicating organelles; includes checkpoints to correct errors in duplicated chromosomes.
- G0 Phase: Non-dividing state that can be permanent.
M-phase: Cell Division
- Mitosis and Cytokinesis
- Mitosis gives rise to two identical daughter cells (2n) from somatic cells.
- Stages of Mitosis:
- Prophase: Chromatin condenses into visible chromosomes; nuclear membrane disintegrates; spindle fibers begin forming.
- Metaphase: Chromosomes align at the metaphase plate; spindle fibers attach to centromeres.
- Anaphase: Chromatids separate and move to opposite poles of the cell as spindle fibers shorten.
- Telophase: Chromatids reach poles and decondense; nuclear membranes reform, and cleavage furrow begins to form.
- Cytokinesis: Final division of the cytoplasm into two daughter cells.
Meiosis: Sexual Cell Division
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Definition and Process
- Meiosis occurs in germ cells, halving chromosome number from diploid (2n) to haploid (n) across two divisions.
- Results in four genetically diverse daughter cells.
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Stages of Meiosis:
- Interphase: Cells undergo a preparatory growth phase, similar to the interphase in mitosis, but DNA is not replicated again.
- Meiosis I:
- Prophase I: Nuclear membrane disintegrates; spindle fibers form; includes crossing over between homologous chromosomes.
- Metaphase I: Homologous chromosomes align at the cell's center.
- Anaphase I: Homologous chromosomes are pulled apart to opposite poles.
- Telophase I: Chromosomes decondense, nuclear membrane reforms; cleavage furrow starts to form.
- Interkinesis: Brief stage without DNA replication where cell growth occurs.
- Meiosis II: Resembles mitosis, separating chromatids similar to mitotic phases (Prophase II, Metaphase II, Anaphase II, Telophase II), resulting in four unique haploid cells.
Key Differences between Mitosis and Meiosis
- Mitosis produces two identical daughter cells (2n).
- Meiosis results in four genetically diverse daughter cells (n).
- Mitosis occurs in somatic cells, whereas meiosis occurs in gametes.
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