Cells and Cell Division
What you must know
Know the major organelles and their functions: nucleus (genome), mitochondria (oxidative phosphorylation, own DNA), rough ER (protein synthesis/folding), smooth ER (lipid synthesis, detox), Golgi (sorting/modification), lysosomes (acidic degradation), ribosomes (translation). Understand the cell cycle: interphase (G1, S, G2) and M phase (mitosis plus cytokinesis). Know the phases of mitosis (prophase, metaphase, anaphase, telophase) and the checkpoints (G1/S, G2/M, spindle) that monitor DNA integrity and chromosome attachment. Distinguish mitosis (diploid daughters, identical) from meiosis (haploid gametes, crossing over in prophase I, independent assortment in metaphase I). Understand that meiosis generates genetic diversity through crossing over and independent assortment.
Traps
Questions may present a cell with replicated chromosomes and ask whether it is in mitosis or meiosis-check ploidy and whether homologs are paired. A common error is confusing the S phase (DNA replication) with the G2/M checkpoint (which verifies replication is complete). Also distinguish apoptosis (programmed, controlled) from necrosis (passive, inflammatory).
Worked rule of thumb
For chromosome-count questions: after S phase, chromosome number is unchanged but each chromosome has two sister chromatids. Count centromeres to count chromosomes; count chromatids separately.
Quick example
A human cell in G2 has 46 chromosomes and 92 chromatids. After meiosis I, each daughter has 23 chromosomes (each with two chromatids); after meiosis II, each gamete has 23 chromosomes with one chromatid.