1. Prophase
2. C
3. A
4. D, A, F, C, E, B
5. Centrosome (or centriole)
6. Animal cells; they have centrosomes/centrioles and undergo cytokinesis by cleavage furrow. a) Plant cells would have cell plates forming during cytokinesis and lack centrosomes.
7. Interphase (specifically the S phase within it is often the longest sub-phase)
8. Mitosis is important for growth, repair, and asexual reproduction, ensuring each daughter cell receives an identical copy of the parent cell's chromosomes.
9. Chromosomes would not separate properly, leading to daughter cells with incorrect chromosome numbers (aneuploidy), which can cause cell death or disease.
10. The cell would not divide into two daughter cells, resulting in a single cell with multiple nuclei (multinucleation).
11. Interphase (including G1, S, G2) occurs before the M phase (mitosis and cytokinesis) shown in the diagrams; it is the preparatory phase where the cell grows and replicates its DNA.
12. [Sketch description: Draw a chromosome with two identical sister chromatids joined at the centromere; label the chromatids and centromere.]
B)
1. Cells go through a cell cycle to grow, replicate their DNA, and divide into two genetically identical daughter cells, enabling organismal growth, development, and tissue repair.
2. No; different cell types divide at different rates depending on their function (e.g., skin and gut cells divide rapidly, while neurons rarely divide).
3. G0 phase is a quiescent state outside the active cell cycle where cells are metabolically active but not preparing to divide; they may re-enter the cycle if stimulated.
4. Cells permanently in G0 are terminally differentiated and perform specialized functions without dividing (e.g., neurons, muscle cells); this prevents uncontrolled proliferation and maintains tissue stability.
5. Label the pie chart: G1, S, G2, M, and optionally G0 as a side branch from G1.
C)
a. G1: Cell growth, protein synthesis, and preparation for DNA replication.
b. S: DNA synthesis/replication; chromosomes are duplicated.
c. G2: Final preparation for mitosis; synthesis of proteins and organelles needed for division.
d. M: Mitosis (nuclear division) followed by cytokinesis (cytoplasmic division); results in two daughter cells.
e. C: Cytokinesis; physical separation of the cytoplasm and organelles into two daughter cells.
f. The two irreversible points are: 1) The restriction point in late G1, after which the cell is committed to completing the cycle even if external signals are withdrawn; 2) The metaphase-to-anaphase transition, once chromosomes are aligned and separated, division cannot be reversed.
Parent Tip: Review the logic above to help your child master the concept of cell cycle worksheet.
