Cell Growth and Division Quiz

Cell Growth and Division

• Organisms reproduce asexually, producing genetically identical offspring.
• Other organisms reproduce sexually, producing diverse offspring.
• Cell division is fundamental to the reproduction of cells and organisms.
• Prokaryotes reproduce asexually by binary fission.
  • This involves chromosome duplication, followed by separation of copies and elongation of the cell, culminating in two daughter cells.

Limits to Cell Growth

• Cells divide due to DNA overload and difficulty exchanging materials across the cell membrane.

The Eukaryotic Cell Cycle and Mitosis

• Eukaryotic cells have multiple chromosomes organized within a nucleus.
• Chromosomes are visible only during cell division; otherwise, chromatin fibers are too small to see.
• Before cell division, chromosomes replicate to form sister chromatids attached at the centromere.
• Mitosis separates sister chromatids to produce two genetically identical daughter cells.
• The cell cycle consists of Interphase and the Mitotic Phase.

Interphase

• The cell grows, duplicates its chromosomes and prepares for division.
  • Includes G1, S, and G2 phases.

Mitotic Phase

• The duplicated chromosomes are distributed into two daughter nuclei. Includes Mitosis (prophase, prometaphase, metaphase, anaphase, telophase) and cytokinesis.

Cytokinesis

• Cytokinesis differs in plant and animal cells.
  • Animal cells divide by a cleavage furrow.
  • Plant cells form a cell plate.
• Cells in culture divide until they touch each other (density-dependent inhibition) requiring attachment to a surface (anchorage dependency)
• Growth factors stimulate cell division in most animal cells.

Cell Cycle Checkpoints

• Proteins control the cell cycle, checking if conditions are suitable for division.
• Signals at checkpoints regulate whether a cell will complete the cycle and divide.
• Growth factor binding to receptors often initiates the cell cycle.

Cell Cycle Phases

• G1 (First Gap): Cell growth and preparation for DNA synthesis.
• S (Synthesis): DNA replication.
• G2 (Second Gap): Organelle synthesis for cell division.
• M (Mitosis): Nuclear division and cytokinesis.

Cancer

• Uncontrolled cell division leads to tumors (masses of cells).
• Malignant tumors can invade and spread (metastasis).

Meiosis and Crossing Over

• Somatic cells have a specific number of chromosomes (e.g., humans have 46, forming 23 pairs).
• Homologous chromosomes have similar genes at the same loci.
• Gametes (sperm and egg) are haploid, with a single set of chromosomes.
• Meiosis I separates homologous chromosomes to form two haploid daughter cells.
• Crossing over exchanges segments between homologous chromosomes during Prophase I.
• Meiosis II separates sister chromatids to yield four haploid gametes.

Independent Orientation and Variety

• The random arrangement of chromosomes during metaphase I leads to diverse combinations of chromosomes in gametes.

Homologous Chromosomes and Crossing Over

• Homologous chromosomes carry different versions of genes.
• Crossing over further increases genetic variability.

Karyotypes and Nondisjunction

• A karyotype is a visual display of an organism's chromosomes that shows an ordered arrangement of chromosomes.
  • Showing abnormalities in the chromosome number and structure.
• Nondisjunction (failure of chromosome separation during meiosis) results in abnormal chromosome numbers.
• Nondisjunction can occur in meiosis I or meiosis II.

Chromosome Abnormalities

• Deletions, duplications, inversions, and translocations are other chromosomal abnormalities.
• Translocations and their significance in cancer. (e.g., "Philadelphia chromosome")