AP Bio Unit 5 Koehler

• G0: Cell cycle arrest (cells that do not undergo mitosis: neurons) 

• G1: Cellular organs are duplicated   

• S: 46 chromosomes are duplicated (DNA synthesis) 

• G2: Preparation for mitosis (Centriole growth) 

• Mitosis: PMAT 

• Cytokinesis: Actual splitting of the cell  

• The structure of the chromosome - where are the chromatids, the centromere, etc. 

• Phases of mitosis and what occurs in each phase 

  • Prophase: Chromosomes condense and become visible, spindle fibers emerge from the centrosomes, the nuclear envelope breaks down and the nucleolus becomes visible 

• Prometaphase: Chromosomes continue to condense, kinetochores appear at the centromeres, microtubules attach to the kinetochores, and the centrosomes move towards opposite poles 

• Metaphase: Mitotic spindle is fully developed, centrosomes are at opposite poles of the cell, the chromosomes line up at the metaphase plate, each sister chromatid is attached to a spindle fiber 

• Anaphase: The cohesin proteins binding the sister chromatids break down, and the sister chromatids (chromosomes) are pulled towards opposite poles. Non-kinetochore spindle fibers lengthen, elongating the cell  

• Telophase: Chromosomes are at opposite poles and begin to decondense, the mitotic spindle breaks down, and nuclear envelope material surrounds each set of chromosomes 

• The general mechanism of binary fission, and what organisms it occurs in

  • Binary fission occurs in prokaryotes and some single-celled eukaryotes that undergo asexual reproduction 

• Relationship between cancer cells and mitosis 

  • If a DNA mutation occurs in the cell and it is not caught at the checkpoint or during mitosis, the cell will keep replicating until there are clumps of mutated cells

  • This creates a tumor and cancerous cells in the body 

• How cytokinesis differs in animals vs. plant cells 

• Checkpoints of the cell cycle

  • After G1: Enough nutrients, proper cell growth 

  • After G2: DNA mutations, proper replication 

  • After Mitosis: Chromosomes attached to spindle, chromatids evenly separated 

• The fate of specialized cells and non-dividing cells in regards to the cell cycle

  • Non-dividing cells: Enter G0 phase of the cell cycle and do not replicate DNA/organelles 

  • Specialized cells: Undergo differential gene expression 

    • Stimulus switches off certain genes in an unspecialized cell 

    • Transcription and translation occur until all the genes in the cell are encoded to produce different proteins 

Meiosis and Sexual Life Cycles (Ch. 10)

• Asexual vs. sexual reproduction

  • Asexual reproduction only requires one parent, sexual reproduction requires two 

    • Asexual: Binary fission (prokaryotes), budding (coral), fragmentation/regeneration (planarians), parthenogenesis 

    • Sexual: Spermatogenesis + Oogenesis

• Relationship between homologous chromosomes, sister chromosomes, and their locations on a karyotype

  • Homologous Chromosomes: Pair of chromosomes that contain the same genes, but potentially different alleles for the genes 

  • Sister Chromatids: Set of duplicated chromatids ( | + | = X)   

  • Karyotype: Each person has 23 homologous pairs of chromosomes and 46 chromosomes 

    • Each chromosome in each pair comes from one parent and the other from the other parent 

• Difference between haploid and diploid cells

  • Haploid (N): Cells do not have full set of chromosomes 

  • Diploid (2N): Cells have full set of chromosomes (homologous chromosomes are with their pairs) 

• The phases of meiosis and what occurs in each stage

  • Prophase I: Chromosomes are with their homologous pair, nuclear envelope dissolves, spindle grows from centrosomes (CROSSING OVER)

  • Metaphase I: Homologous pairs line up in the center, microtubules attach to kinetochores 

  • Anaphase I: Homologous pairs are pulled apart 

  • Telophase I: Cleavage furrow appears and cell pinches together  

  • Cytokinesis: Cell separates into two haploid cells 

• PMAT II: Same as mitosis, except all cells are unique due to crossing over 

• Comparisons between mitosis and meiosis

• How independent assortment, crossing over, and random fertilization create genetic diversity

  • Independent Assortment: Different genes independently separate from one another when reproductive cells develop AKA an allele that a gamete receives for one gene does not affect the allele received by another for another gene 

  • Crossing Over: Creates genetic variation in the alleles received by the daughter cells 

  • Random Fertilization: Any random combination of genes from each parent cell 

• Difference between gametes and somatic cells

  • Gametes: Sex cells

  • Somatic: Body cells 

Reproduction and Development (Ch. 36)

• Adaptations other animals have for fertilization, such as parthenogenesis and external fertilization

  • Parthenogenesis: Non-mammalian females undergo parthenogenesis to produce all male offspring 

    • Komodo dragon females give eggs half of the necessary chromosomes but somehow they end up with a full set of DNA (??)

    • External Fertilization: Aquatic females, for example, lay eggs and then various males fertilize them (frogs??)

• The processes of gametogenesis, such as spermatogenesis and oogenesis

  • Spermatogenesis: Same as meiosis, produces 4 sperm cells

  • Oogenesis: Same as meiosis, produces 1 egg and 3 polar bodies 

    • Before puberty: Oocyte stopped during prophase I

    • Puberty → Menopause: Primary oocyte splits into polar body (that splits into 2 polar bodies)  and secondary oocyte 

    • Meiosis II is completed only when fertilized, secondary oocyte splits into ovum third polar body 

• Embryonic development from fertilization, including cleavage and gastrulation

Cell Signaling (5.6)

• The four types of cell signaling

  • Autocrine: Cell signalling itself

  • Paracrine: Nearby cells

  • Endocrine: Long-distance (different areas of the body) 

  • Juxtacrine: Touching cells 

• The three stages of cell signaling

1. Reception: Ligand binds to the receptor (intracellular or extracellular) 

   1. Intracellular ligands: Nonpolar

   2. Extracellular ligand: Polar 

2. Transduction: Series of steps that relays signal from ligand to nucleus (phosphorylation cascades, amplification, or secondary messengers) 

   1. Phosphorylation Cascade: When a protein is phosphorylated, it is activated → when phosphate group is removed, it is inactive 

2. Amplification: Allows multiple responses from one ligand 

3. Secondary Messengers: Offer a second (similar but not the same) pathway 

3. Response: Takes place in the nucleus and involves transcription and translation. (turning off/on genes) 

   How signal transduction pathways differ in single-celled organisms vs. multicellular organisms:

   Examples of cell signaling in context, such as in the immune and nervous systems