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General Biology: Cell Cycle, Mitosis & Meiosis

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  • Asexual Reproduction

    Involves a single parent. Offspring are genetically identical clones produced by budding, fission, or fragmentation.

  • Sexual Reproduction

    Involves two parents contributing gametes. Offspring have unique gene combinations, increasing genetic variation.

  • Binary Fission in Prokaryotes

    Prokaryotes replicate their single circular chromosome, elongate, then divide into two genetically identical daughter cells.

  • Prokaryotic vs. Eukaryotic Chromosomes

    Prokaryotes have a single circular chromosome in the nucleoid; eukaryotes have multiple linear chromosomes in a nucleus.

  • Stages of the Eukaryotic Cell Cycle

    Interphase (G1, S, G2) for growth and DNA replication; Mitotic phase (Mitosis and Cytokinesis) for cell division.

  • G1 Phase

    Cell grows and performs normal functions before DNA replication.

  • S Phase

    DNA is replicated; each chromosome forms sister chromatids.

  • G2 Phase

    Cell continues to grow and prepares for mitosis.

  • Phases of Mitosis

    Prophase, Prometaphase, Metaphase, Anaphase, Telophase; chromosomes condense, align, separate, and nuclei reform.

  • Cytokinesis in Animal Cells

    Occurs via a cleavage furrow where a contractile ring pinches the cell into two.

  • Cytokinesis in Plant Cells

    Occurs via a cell plate formed by vesicles that create a new cell wall between daughter cells.

  • Cancer Cells vs. Healthy Cells

    Cancer cells divide uncontrollably, ignore growth signals, and can invade tissues; healthy cells divide only when needed.

  • Benign vs. Malignant Tumors

    Benign tumors stay localized; malignant tumors invade tissues and spread (metastasize).

  • Somatic Cells

    Body cells that are diploid (2n), containing pairs of homologous chromosomes; humans have 2n = 46.

  • Gametes

    Sex cells (egg and sperm) that are haploid (n), containing one set of chromosomes; humans have n = 23.

  • Diploid vs. Haploid

    Diploid (2n) cells have two chromosome sets; haploid (n) cells have one set.

  • Meiosis I Key Events

    Homologous chromosomes pair and separate, crossing over occurs, resulting in two haploid cells with duplicated chromosomes.

  • Meiosis II Key Events

    Sister chromatids separate, producing four genetically unique haploid cells.

  • Differences Between Mitosis and Meiosis

    Mitosis: one division, no homolog pairing, produces 2 diploid identical cells. Meiosis: two divisions, homolog pairing, crossing over, produces 4 haploid unique cells.

  • Sources of Genetic Variation in Meiosis

    Independent orientation at metaphase I, crossing over in prophase I, and random fertilization.

  • Nondisjunction

    Failure of chromosome pairs or sister chromatids to separate during meiosis, causing abnormal chromosome numbers in gametes.

  • Main Types of Chromosomal Alterations

    Deletion, duplication, inversion, and translocation of chromosome fragments.

  • Inheritance of Cancer Mutations

    Most cancer mutations occur in somatic cells and are not inherited; only germline mutations are passed to offspring.

  • Number of Possible Gamete Combinations

    Calculated as \(2^n\), where \(n\) is the haploid chromosome number.

  • Human Haploid Number and Gamete Combinations

    Humans have \(n=23\), so possible gamete combinations are \(2^{23}\).