The Cell Cycle and Cell Division Flashcards
(10 cards)
What are the stages of mitosis?
Prophase: Chromosomes condense, spindle forms
Metaphase: Chromosomes align at metaphase plate
Anaphase: Sister chromatids separate to opposite poles
Telophase: Chromosomes decondense, nuclear envelope reforms
Cytokinesis: Cytoplasm divides, forming two daughter cells
Why does DNA appearance change from interphase to mitosis?
DNA condenses into tightly packed chromosomes in mitosis to prevent tangling and ensure accurate segregation; in interphase, it is loosely packed (chromatin) to allow gene expression and replication.
How do CDKs and cyclins regulate the cell cycle?
Cyclins bind and activate CDKs (cyclin-dependent kinases)
Different cyclin-CDK complexes trigger progression through checkpoints (G₁/S, G₂/M) by phosphorylating target proteins
Define oncogene, proto-oncogene, and tumor suppressor.
Proto-oncogene: Normal gene that promotes cell growth/division
Oncogene: Mutated proto-oncogene → causes uncontrolled growth
Tumor suppressor: Gene that inhibits cell cycle or promotes repair; loss of function contributes to cancer
How does BRCA1 relate to DNA repair and the cell cycle?
BRCA1 helps repair double-strand DNA breaks via homologous recombination; mutations in BRCA1 impair repair and can lead to unchecked division and cancer.
How do changes in cell cycle regulation contribute to cancer?
Mutations in oncogenes or tumor suppressors can lead to uncontrolled cell division, evasion of checkpoints, and accumulation of DNA damage—hallmarks of cancer.
What is the difference between homologous chromosomes and sister chromatids?
Homologous chromosomes: One from each parent; same genes, possibly different alleles
Sister chromatids: Identical copies of a single chromosome made during S phase, held together at the centromere
How do homologous chromosomes and sister chromatids behave during mitosis?
Sister chromatids are separated in anaphase of mitosis
Homologous chromosomes do not pair or segregate in mitosis (that happens in meiosis)
How would drugs that disrupt mitosis affect cell growth?
Drugs that disrupt spindle formation or chromosome separation (e.g., taxol, colchicine) arrest cells in mitosis and can trigger apoptosis → used in cancer therapy
How would mutations that affect cell cycle regulators influence cell growth and division?
Mutations in cyclins, CDKs, or checkpoint proteins can lead to uncontrolled proliferation
Examples: p53 loss removes G₁ checkpoint → damaged cells divide; Rb inactivation allows excessive entry into S phase
