Questions and Answers
What is characteristic of prophase II in meiosis?
During which stage of meiosis do the chromosomes line up at the equatorial plane oriented perpendicularly to the previous orientation?
What occurs during anaphase II of meiosis?
In telophase II, what major structural change occurs?
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Which process contributes to genetic variation during meiosis?
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What is the result of the separation of sister chromatids during anaphase II?
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What happens to chromosomes during metaphase II compared to metaphase I?
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What role do sister kinetochores play during meiosis?
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How does the structure of chromosomes in telophase II differ from that in prophase II?
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Study Notes
Student Learning Outcomes
- Ability to list key phases of Mitosis chronologically.
- Capability to narrate key processes occurring at each mitosis phase.
- Proficient in determining the correct order of phases in meiosis.
- Skill to compare phases of mitosis and meiosis.
Introduction to the Cell Division Cycle
- Non-dividing cells exist in INTERPHASE, lasting from hours to years.
- Cell division occurs in MITOSIS, alternating with interphase in the cell cycle.
- Mitosis represents the M-phase, lasting 1-2 hours.
Stages of the Cell Cycle
- Mitosis is the most visible part of the cell cycle, reflecting the active division.
Rapidly Cycling Cells
- Rapidly dividing cells, like embryonic and tumor cells, often skip G1.
- In mammalian early development, G1 and G2 phases are absent.
G0 Phase
- G1 phase can extend significantly in cells like hepatocytes, lasting up to a year.
- Terminally differentiated cells, e.g., muscle and nerve cells, enter a non-cycling G0 state.
Cell Division (Mitosis)
- Mitosis encompasses two main events: karyokinesis (nuclear division) and cytokinesis (cytoplasmic division).
- Key stages of Mitosis: Prophase, Metaphase, Anaphase, Telophase.
Chromosome Dynamics in Mitosis
- Prior to mitosis, DNA duplicates during the S-phase, resulting in 46 chromosomes (4N).
- Each chromosome comprises sister chromatids linked at the centromere.
Mitosis - Prophase
- Chromatin coils, making chromosomes visible.
- Centrioles separate and migrate to opposite poles; spindle microtubules form.
Mitosis - Late Prophase
- The nucleolus fades and the nuclear membrane disintegrates.
Mitosis - Metaphase
- Chromosomes align at the spindle's equatorial plane.
- Final disappearance of the nuclear envelope and nucleolus.
Mitosis - Early Anaphase
- Chromosomes split into sister chromatids at the kinetochore.
- Sister chromatids migrate to opposite poles.
Mitosis - Late Anaphase
- Further separation of poles occurs; proteins binding sister chromatids inactivate.
- Cleavage furrow formation marks cell preparation for division.
Mitosis - Telophase
- Arrives as chromosomal movement ceases; nuclei reappear in daughter cells.
- Chromosomes relax to a semi-disperse state; nuclear envelope and nucleoli reconstitute.
Cytokinesis
- Cleavage furrow progresses and separates the cytoplasm and organelles, completing cell division.
Meiosis - General Overview
- Meiosis includes two rounds of division: Meiosis I and Meiosis II, with no intervening S-phase.
- Produces four cells, each haploid (n), containing half the original chromosome number (2n to n).
Meiosis - Symbols & Terminology
- Diploid: 46 chromosomes or 2n; Haploid: 23 chromosomes or n.
- DNA in diploid cells is 2N before S-phase and 4N after.
Meiosis - Prophase I
- Chromosomes become visible and doubled; occurs after S-phase.
- Non-sister chromatids can exchange segments in a process known as crossing over (chiasmata formation).
Meiosis - Metaphase I
- Microtubules attach to sister kinetochores of homologues, pulling sister chromatids toward opposite poles.
Meiosis - Prophase II
- Chromosomes, now with a haploid number, condense again, with sister chromatids still attached at the centromere.
Meiosis - Metaphase II
- Chromosomes align at the equatorial plane perpendicular to Metaphase I.
Meiosis - Anaphase II
- Centromeres separate, and sister chromatids are pulled apart to opposite poles by the spindle.
Meiosis - Telophase II
- Sister chromatids reach the poles, and nuclear envelopes form around each nucleus, followed by chromosome uncoiling.
Genetic Recombination
- Meiosis preserves genome size while introducing genetic diversity through three mechanisms.
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Description
Test your knowledge on the key phases of mitosis and meiosis, including their processes and comparisons. This quiz will help you understand the chronological order and crucial functions during cell division and interphase effectively.
