Meiosis: Metaphase 1 and Crossing Over
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Questions and Answers

What occurs during metaphase 1 of meiosis?

  • Sister chromatids line up at the metaphase plate
  • Chromosomes are duplicated for the first time
  • Homologous chromosomes align at the metaphase plate (correct)
  • Crossing over occurs between sister chromatids

    • What is a primary outcome of crossing over during meiosis?

  • It enhances genetic variation (correct)
  • It reduces the number of chromosomes
  • It assists in chromosome duplication
  • It eliminates genetic recombination

    • What is the chromosome number after meiosis I?

  • 2n = 6
  • n = 3 (correct)
  • n = 6
  • 2n = 12

    • Which phase of meiosis involves the lining up of tetrads?

    <p>Meiosis I</p> Signup and view all the answers

    What happens to the chromosome number during meiosis II?

    <p>It remains constant as n = 3</p> Signup and view all the answers

    Which of the following is a difference between meiosis I and meiosis II?

    <p>Synapsis occurs only in meiosis I</p> Signup and view all the answers

    What type of cells are produced by meiosis?

    <p>Gametes</p> Signup and view all the answers

    What is assumed about chromosomes before the S phase?

    <p>Chromosomes are single as 2n = 6</p> Signup and view all the answers

    What is the primary role of the cytoskeleton in a cell?

    <p>To support the cell structure and facilitate movement</p> Signup and view all the answers

    Which protein forms the microfilaments of the cytoskeleton?

    <p>Actin</p> Signup and view all the answers

    What structure do microtubules assemble into during cell division?

    <p>Spindle fibers</p> Signup and view all the answers

    Where are microtubule organizing centers (MTOCs) located in animal cells?

    <p>Centrosomes</p> Signup and view all the answers

    What does the cytoplasm contain?

    <p>All other cellular contents suspended between the nucleus and plasma membrane</p> Signup and view all the answers

    How do microtubules contribute to the strength of skin cells?

    <p>By incorporating keratin into their structure</p> Signup and view all the answers

    What is the characteristic of a cell wall in relation to water?

    <p>It is permeable to water, facilitating transport</p> Signup and view all the answers

    Which of the following describes the arrangement of microtubules?

    <p>In rows with 13 tubulin dimers surrounding a central core</p> Signup and view all the answers

    What is the primary composition of phloem?

    <p>Sieve-tube elements</p> Signup and view all the answers

    What characterizes collenchyma cells?

    <p>Provide flexible support to immature parts of plants</p> Signup and view all the answers

    Which type of sclerenchyma cell is responsible for the gritty texture of some fruits?

    <p>Sclereids</p> Signup and view all the answers

    What is the role of xylem in plants?

    <p>Transporting water and minerals</p> Signup and view all the answers

    Which structure on epithelial cells is made of actin microfilaments?

    <p>Microvilli</p> Signup and view all the answers

    Which of the following cells undergoes a process of modification resulting in the loss of organelles like the nucleus?

    <p>Red blood cells</p> Signup and view all the answers

    What type of permanent tissue is primarily responsible for providing structural support and rigidity to plants?

    <p>Sclerenchyma</p> Signup and view all the answers

    How do nutrients and organic compounds get distributed throughout a plant?

    <p>Through both phloem and xylem</p> Signup and view all the answers

    What is the primary role of the cytoplasm in a cell?

    <p>It serves as a vessel for various cellular functions.</p> Signup and view all the answers

    Which statement accurately describes the cytosol?

    <p>It is a semifluid solution consisting of water and molecules.</p> Signup and view all the answers

    What is the relationship of endosymbiotic theory to mitochondria and chloroplasts?

    <p>They originated from independent prokaryotes engulfed by a eukaryotic cell.</p> Signup and view all the answers

    Which component of the cell acts as a barrier and maintains shape?

    <p>Cell wall</p> Signup and view all the answers

    What prevents plant cells from bursting due to excessive water absorption?

    <p>Cell wall</p> Signup and view all the answers

    Which function is primarily performed by the cytoskeleton within the cell?

    <p>Cell shape maintenance</p> Signup and view all the answers

    What is the composition of cytoplasm?

    <p>A semifluid solution containing water and various molecules</p> Signup and view all the answers

    Which of the following best describes prokaryotic cells in relation to the cell wall?

    <p>Most prokaryotic cells, including bacteria and archaea, possess a rigid cell wall.</p> Signup and view all the answers

    What is the main purpose of meiosis in the formation of gametes?

    <p>To produce cells with half the chromosome number</p> Signup and view all the answers

    During which phase do homologous chromosomes separate?

    <p>Anaphase I</p> Signup and view all the answers

    What occurs during Prophase I?

    <p>Condensation of chromosomes</p> Signup and view all the answers

    What is the primary difference between meiosis I and meiosis II?

    <p>Meiosis I is a reductional division, while meiosis II is an equational division</p> Signup and view all the answers

    What happens during Telophase I?

    <p>The cytoplasm divides</p> Signup and view all the answers

    Which phase follows cytokinesis in meiosis II?

    <p>Prophase II</p> Signup and view all the answers

    Which of the following correctly describes crossing over?

    <p>It involves the exchange of genetic material between homologous chromosomes</p> Signup and view all the answers

    What occurs during Metaphase II?

    <p>Sister chromatids line up at the equator</p> Signup and view all the answers

    Study Notes

    Meiosis Overview

    • Meiosis results in the formation of gametes through two rounds of division: Meiosis I and Meiosis II.
    • In Meiosis I, homologous chromosomes align at the metaphase plate while sister chromatids remain attached.
    • After Meiosis I, the chromosomal number is reduced (from 2n = 6 to n = 3).

    Importance of Crossing Over

    • Crossing over during prophase I facilitates genetic recombination, enhancing genetic variation and increasing survival chances.

    Changes in Chromosome Number

    • Before S phase, chromosomes are single (2n = 6) during the G1 phase.
    • After S phase, duplicated chromosomes are present (still 2n = 6).
    • During Meiosis II, sister chromatids are separated, resulting in n = 3.

    Mitosis vs. Meiosis

    • Mitosis maintains identical genetic material in daughter cells, while meiosis reduces genetic material and introduces variability.
    • Key differences include:
      • Synapsis only occurs in Meiosis I.
      • Tetrads align during Meiosis I, not in Meiosis II.
      • Crossing over is exclusive to Meiosis I.

    Cytoskeleton Structure and Function

    • Microtubules form spindle fibers essential for cell division, anchoring chromosomes during mitosis and meiosis.
    • Microfilaments, composed of actin, provide support, maintain cell shape, and allow movement.

    Cytoplasm and Cell Structure

    • The cytoplasm contains organelles suspended in cytosol—a semifluid solution comprised of water and organic molecules.
    • Major components of the cell include the plasma membrane, cytoplasm, cytoskeleton, and cell wall.

    Cell Wall Characteristics

    • The cell wall is a rigid structure primarily found in prokaryotes, providing shape and preventing excessive water absorption.

    Specialized Plant Cells

    • Collenchyma offers flexible support to young plant parts without lignin in primary walls.
    • Sclerenchyma provides rigidity with two types: sclereids (strengthening seeds) and fibers (used commercially).

    Xylem and Phloem Function

    • Xylem transports water and minerals, while phloem distributes organic nutrients throughout the plant.

    Microvilli and Their Role

    • Microvilli, extensions of epithelial cells, enhance surface area and contain actin microfilaments for structural support.

    Meiosis Phases

    • Meiosis involves:

      • Prophase I: Chromosome condensation and synapsis.
      • Metaphase I: Chromosomes align at the equator.
      • Anaphase I: Homologous pairs separate.
      • Telophase I: Cytoplasm divides, producing two daughter cells.

    • During Meiosis II, a second cycle occurs without further chromosome reduction, resembling a mitotic division.

    Endosymbiotic Theory

    • Mitochondria and chloroplasts are believed to have originated from engulfed prokaryotes, evident from their double membranes and independent genetic material.

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    Description

    This quiz covers the critical phase of meiosis known as metaphase 1, where homologous chromosomes align at the metaphase plate. Additionally, it discusses the importance of crossing over in facilitating genetic recombination and enhancing genetic variation.

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