Chapter 10: Cell Reproduction Flashcards
Why do cells divide?
For growth, repair, reproduction (in unicellular organisms), and to maintain efficient surface area-to-volume ratios.
Compare mitosis and meiosis.
Mitosis: Produces 2 genetically identical diploid (2n) somatic cells.
Meiosis: Produces 4 genetically diverse haploid (n) gametes.
What is the cell cycle?
The ordered sequence of events from cell formation to division: Interphase (G1, S, G2) → Mitosis (M phase) → Cytokinesis.
Describe the phases of interphase.
G1 (Gap 1): Cell growth and organelle duplication.
S (Synthesis): DNA replication.
G2 (Gap 2): Preparation for mitosis (e.g., protein synthesis).
What happens during the S phase?
DNA replicates, producing sister chromatids held together at the centromere.
What are cell cycle checkpoints?
Control points ensuring proper completion of each phase:
G1 Checkpoint: Checks for DNA damage and nutrient availability.
G2 Checkpoint: Verifies DNA replication.
M Checkpoint (Spindle): Ensures chromosomes attach to spindle fibers.
List the stages of mitosis in order.
Prophase → Prometaphase → Metaphase → Anaphase → Telophase (PMAT).
What occurs during prophase?
Chromatin condenses into chromosomes.
Nuclear envelope breaks down.
Spindle fibers form from centrosomes.
What is the role of the kinetochore?
Protein structure on chromatids where spindle fibers attach to pull chromosomes apart.
What happens during anaphase?
Sister chromatids separate and move to opposite poles (shortest phase).
Define cytokinesis.
Division of the cytoplasm. In animal cells, a cleavage furrow forms; in plant cells, a cell plate forms.
What are cyclins and CDKs?
Cyclins: Regulatory proteins that fluctuate during the cycle.
CDKs (Cyclin-Dependent Kinases): Enzymes activated by cyclins to drive phase transitions.
What is the role of p53?
Tumor suppressor protein that halts the cell cycle at G1 if DNA is damaged, allowing repair or apoptosis.
How does cancer relate to cell cycle regulation?
Mutations in proto-oncogenes (e.g., Ras) or tumor suppressors (e.g., p53) lead to uncontrolled division.
What is the purpose of meiosis?
To produce haploid gametes (sperm/eggs) with genetic diversity via crossing over and independent assortment.
Describe the stages of meiosis I and II.
Meiosis I: Homologous chromosomes separate (reductional division).
Meiosis II: Sister chromatids separate (equational division).
What is crossing over? When does it occur?
Exchange of genetic material between homologous chromosomes during prophase I, increasing genetic diversity.
Define independent assortment.
Random alignment of homologous pairs at metaphase I, leading to 2²³ possible chromosome combinations in humans.
What are stem cells?
Undifferentiated cells capable of self-renewal and differentiation into specialized cells (e.g., embryonic stem cells).
Compare totipotent, pluripotent, and multipotent stem cells.
Totipotent: Can form any cell type + extraembryonic tissues (e.g., zygote).
Pluripotent: Can form any cell type (e.g., embryonic stem cells).
Multipotent: Limited to specific lineages (e.g., hematopoietic stem cells).
How do telomeres affect cell division?
Telomeres shorten with each division; telomerase (in stem cells/germ cells) lengthens them to prevent DNA loss.
What is apoptosis? How is it regulated?
Programmed cell death triggered by internal (e.g., DNA damage) or external signals (e.g., TNF). Regulated by Bcl-2 proteins and caspases.
What is binary fission?
Asexual reproduction in prokaryotes: DNA replicates → cell elongates → splits into two (e.g., bacteria).
How do checkpoint failures lead to cancer?
Defective checkpoints allow cells with DNA damage to divide, accumulating mutations (e.g., BRCA1 mutations in breast cancer).
