Biology Chapter on Cell Division
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Questions and Answers

What is a characteristic of asexual reproduction?

  • Involves two gametes joining to form a zygote
  • Produces two identical daughter cells (correct)
  • Occurs exclusively in multicellular organisms
  • Results in genetically diverse offspring

    • During which phase of the cell cycle is DNA replicated?

  • S Phase (correct)
  • M Phase
  • G1 Phase
  • G2 Phase

    • In prokaryotic cell division, what process is used to create two identical cells?

  • Mitosis
  • Cytokinesis
  • Meiosis
  • Binary fission (correct)

    • Which stage follows the synthesis stage (S) in the cell cycle?

    <p>G2 Phase</p> Signup and view all the answers

    What happens during the G1 stage of interphase?

    <p>Cells grow and produce organelles</p> Signup and view all the answers

    What key process occurs during the G2 phase of interphase?

    <p>Production of structures for cell division</p> Signup and view all the answers

    What is formed between replicates of the chromosome during binary fission in prokaryotes?

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

    Which of the following correctly describes mitosis?

    <p>Is a form of asexual reproduction</p> Signup and view all the answers

    What is the role of fertilization in sexual reproduction?

    <p>It restores the diploid chromosome number.</p> Signup and view all the answers

    What occurs during the S phase of Interphase?

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

    What are sister chromatids?

    <p>Replicated chromosomes that have the same alleles.</p> Signup and view all the answers

    What is the outcome of meiosis in terms of chromosome number?

    <p>Meiosis reduces the chromosome number to haploid.</p> Signup and view all the answers

    How do homologous chromosomes differ from sister chromatids?

    <p>They contain different alleles for the same genes.</p> Signup and view all the answers

    What is the primary reason for new cell production in organisms?

    <p>To replace damaged or old cells</p> Signup and view all the answers

    How do prokaryotic chromosomes differ from eukaryotic chromosomes?

    <p>Prokaryotic DNA is a single circular chromosome, while eukaryotic DNA is organized into multiple linear chromosomes</p> Signup and view all the answers

    What occurs during DNA replication before cell division?

    <p>DNA is copied to create two identical strands</p> Signup and view all the answers

    What is the structure that holds together duplicated chromosomes?

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

    In a human cell, how are the chromosomes typically organized?

    <p>In pairs arranged by size in a karyotype</p> Signup and view all the answers

    What is the role of histones in relation to DNA?

    <p>To help compact DNA into chromosomes</p> Signup and view all the answers

    What is the typical number of chromosomes found in human body cells?

    <p>46 chromosomes</p> Signup and view all the answers

    What occurs during crossing-over in prophase I?

    <p>Homologous chromosomes exchange genetic material.</p> Signup and view all the answers

    What is formed when homologous chromosomes pair during prophase I?

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

    What characterizes anaphase I of meiosis?

    <p>Homologs separate and move to opposite poles.</p> Signup and view all the answers

    What is the main purpose of meiosis I?

    <p>Reduce the chromosome number from diploid to haploid.</p> Signup and view all the answers

    Which of the following occurs during late prophase I?

    <p>Homologous chromosomes condense and form tetrads.</p> Signup and view all the answers

    What happens to the nuclear envelope during prophase I?

    <p>It fragments.</p> Signup and view all the answers

    At the end of meiosis I, how many homologs of each chromosome are present in the resulting cells?

    <p>One homolog</p> Signup and view all the answers

    Which process greatly increases genetic variety during the formation of gametes?

    <p>Independent assortment and crossing-over</p> Signup and view all the answers

    What is the process called when the cell divides its nucleus?

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

    During which stage of mitosis do chromosomes align at the cell's equator?

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

    What structure is responsible for attaching to the centromere of each chromosome?

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

    What occurs during telophase of mitosis?

    <p>The nuclear envelope forms around the sister chromatids</p> Signup and view all the answers

    What is cytokinesis?

    <p>Division of the cell's cytoplasm</p> Signup and view all the answers

    Which statement is true regarding the daughter cells produced after mitosis?

    <p>They are smaller than the parent cell.</p> Signup and view all the answers

    Which stage of mitosis is characterized by the breakdown of the nuclear membrane?

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

    What structure forms in plant cells during cytokinesis?

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

    What happens to chromosomes during anaphase?

    <p>They are separated and pulled towards opposite poles.</p> Signup and view all the answers

    What characterizes the late prophase stage of mitosis?

    <p>The nuclear membrane and nucleolus disintegrate.</p> Signup and view all the answers

    What occurs during crossing over in meiosis I?

    <p>Sister chromatids may carry non-identical genetic information.</p> Signup and view all the answers

    What is the outcome of meiosis II?

    <p>Four genetically different haploid cells are produced.</p> Signup and view all the answers

    Why do polar bodies typically die during oogenesis?

    <p>They result from unequal division of cytoplasm.</p> Signup and view all the answers

    How many sperm are produced per day by men?

    <p>250,000,000 sperm</p> Signup and view all the answers

    What is the primary result of meiosis in terms of genetic variation?

    <p>Gametes have one allele of each gene.</p> Signup and view all the answers

    Which phase of meiosis II involves the separation of sister chromatids?

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

    What distinguishes oogenesis from spermatogenesis?

    <p>Oogenesis creates only one viable gamete.</p> Signup and view all the answers

    How many divisions are involved in meiosis compared to mitosis?

    <p>1 division in mitosis, 2 in meiosis</p> Signup and view all the answers

    Which statement about gametes is true following meiosis?

    <p>They are haploid, containing one copy of each chromosome.</p> Signup and view all the answers

    Study Notes

    Cell Division

    • All cells originate from pre-existing cells.
    • New cells are created for growth and to replace damaged or old cells.
    • Cellular division differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, and animals).

    Maintaining Identical Cells

    • Instructions for cell parts are encoded in the DNA.
    • Each new cell must receive a complete set of DNA molecules.
    • DNA must be duplicated (replicated) before cell division.
    • Each new cell will have an identical copy of the original DNA.

    Identical Daughter Cells

    • The result of cell division is two identical daughter cells.
    • Daughter cells inherit the same genetic information.

    Chromosomes

    • Prokaryotes have one circular chromosome located inside the cell membrane.
    • Eukaryotic cells store genetic information in chromosomes, ranging from 10 to 50 per cell in most eukaryotes.
    • Humans have 46 chromosomes (or 23 identical pairs).
    • Chromosomes are composed of tightly coiled DNA molecules.
    • In non-dividing cells, chromosomes are uncondensed, forming chromatin.
    • DNA is tightly coiled around proteins called histones to compact DNA into chromosomes.

    Chromosomes in Dividing Cells

    • Duplicated chromosomes are called chromatids and are held together by a centromere.
    • Sister chromatids are identical copies of a chromosome.

    Karyotype

    • A karyotype is a picture of chromosomes arranged by size in pairs.
    • The first 22 pairs of chromosomes are called autosomes, and the last pair are sex chromosomes (XX for females and XY for males).

    Cell Reproduction

    • Asexual reproduction involves a single cell dividing to yield two new, identical daughter cells. Mitosis and binary fission are examples.
    • Sexual reproduction involves two cells (sperm and egg) merging to create a new cell (zygote) which is not identical to the original cells. Meiosis is part of this process.

    Prokaryotic Cell Division - Binary Fission

    • Prokaryotes, like bacteria, divide by a process called binary fission.
    • A single chromosome makes a copy of itself.
    • A cell wall forms between the chromosomes, dividing the cell.
    • The cell splits, creating two identical daughter cells.

    The Cell Cycle

    • Consists of five distinct phases: G1, S, G2, M, and C.
    • G1 - Primary growth phase.
    • S - Synthesis phase, DNA is replicated.
    • G2 - Secondary growth phase, preparing for division. Collectively, these three phases are called interphase.
    • M - Mitosis, division of the nucleus (karyokinesis).
    • C - Cytokinesis, division of the cytoplasm.

    Interphase - G1 Stage

    • The first growth stage after cell division.
    • Cell maturation through increasing cytoplasm and organelles.
    • Normal metabolic activities occur.

    Interphase - S Stage

    • Synthesis stage.
    • DNA is copied or replicated.

    Interphase - G2 Stage

    • Second growth stage, following DNA replication.
    • Cells form the necessary structures for division (e.g., centrioles).
    • Synthesis of organelles and proteins.

    Mitosis

    • Division of the nucleus.
    • Also known as karyokinesis.
    • Eukaryotes only.
    • Four phases: prophase, metaphase, anaphase, and telophase.

    Early Prophase

    • Chromatin condenses to form visible chromosomes.
    • Mitotic spindle forms (in animal cells, from the centrioles).

    Late Prophase

    • Nuclear membrane and nucleolus disappear.
    • Chromosomes continue condensing and become clearly visible.
    • Spindle fibers (kinetochores) attach to the centromere of each chromosome.
    • Spindle fibers complete development between cell poles.

    Metaphase

    • Chromosomes align along the cell's equator (metaphase plate).

    Anaphase

    • Centromeres divide, sister chromatids separate to opposite poles of the cell.
    • Kinetochore fibers shorten.

    Telophase

    • Sister chromatids reach opposite poles of the cell.
    • Spindle fibers disassemble.
    • Nuclear envelopes re-form around each set of separated chromosomes and nucleoli reappear.
    • Chromosomes decondense back to chromatin.
    • Cytokinesis occurs (cytoplasmic division).

    Cytokinesis

    • The cytoplasm divides into two identical daughter cells.
    • In plants, a cell plate forms at the cell's equator to divide.
    • In animals, a cleavage furrow forms to pinch the cell in two.

    Mitosis Stages

    • Prophase: Chromosomes condense, nuclear envelope disappears, spindle apparatus forms.
    • Metaphase: Chromosomes align at the metaphase plate.
    • Anaphase: Sister chromatids separate and move to opposite poles.
    • Telophase: Chromosomes decondense, nuclear envelope reforms, spindle apparatus breaks down.

    Daughter Cells of Mitosis

    • Daughter cells have the same number of chromosomes as the parent cell.
    • They are identical to each other but are initially smaller than the parent cell.
    • They grow in size to become mature cells (G1 of interphase).

    Meiosis

    • Cell division that produces gametes (sperm and egg).
    • Preceded by interphase, which involves chromosome replication.
    • Two meiotic divisions (Meiosis I and Meiosis II).
    • Reduces the chromosome number by half.
    • Original (parent) cell is diploid (2n).
    • Four daughter cells are produced, each haploid (1n).

    More Meiosis Facts

    • Begins with 46 double-stranded chromosomes (2n).
    • After meiosis I, the result is 23 double-stranded chromosomes (n).
    • After meiosis II, the result is 23 single-stranded chromosomes (n) in four daughter cells.
    • Occurs in germ cells that produce gametes.

    Why Meiosis?

    • The basis of sexual reproduction.
    • Haploid gametes (n) fuse during fertilization to create a diploid zygote (2n).

    Spermatogenesis

    • Occurs in the testes; producing sperm.
    • Two divisions yield four spermatids.
    • Spermatids develop into sperm.
    • Men produce approximately 250 million sperm per day.

    Oogenesis

    • Occurs in the ovaries, producing eggs.
    • Two divisions produce one egg and three polar bodies.
    • Polar bodies die because of unequal cytoplasm division.

    Comparing Mitosis and Meiosis

    • Mitosis: one division, two identical diploid daughter cells, growth and repair. Meiosis: two divisions, four genetically unique haploid daughter cells, sexual reproduction.

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    Description

    This quiz covers key concepts related to cell division, including asexual reproduction, the cell cycle phases, DNA replication, and the differences between prokaryotic and eukaryotic chromosomes. Test your understanding of mitosis, meiosis, and the overall processes that lead to new cell production.

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