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This chapter should help the student to:

  • List the names and functions of the nuclear components.

  • List the subunits of each nuclear component and their functions.

  • Explain the process of cell division and its effects on cell structure.

  • Identify the factors and activities controlling the transition from each cell-cycle phase to the next.

  • Recognize a cell’s nuclear components in a light or electron photomicrograph and hence predict the cell’s relative activity.

  • Predict a cell’s nuclear appearance from its functional characteristics.

  • Predict the functional deficits accompanying specific nuclear or chromosomal aberrations.

  • Predict the nuclear component(s) likely to be involved in a functional deficit.

  • Explain the role of the nucleus in cell differentiation.


  1. List the four major structural components of a nucleus (I.A1).

  2. Explain why the term “nuclear envelope” is more appropriate than “nuclear membrane” (II).

  3. List the substances and structures associated with the nuclear envelope’s internal and external surfaces (II.A and B).

  4. Name the components of a nuclear pore complex and indicate which anchors the complex in the envelope and which form its walls as it penetrates the envelope (II.C).

  5. List several important macromolecules that must traverse the nuclear pores for basic cell functions to be carried out (II.C).

  6. Compare euchromatin and heterochromatin (III.B and C) in terms of their appearance in light and electron microscopy, degree of coiling, and involvement in transcriptional activity.

  7. List the components of a nucleosome (III.A).

  8. List the parts of a nucleolus and relate them to its function (IV.A, B.1 and 2).

  9. In which cell types would you expect to find particularly large or abundant nucleoli (IV)?

  10. List in order, the phases of mitosis and sketch the appearance and location of the chromosomes during each phase (VI.A.2.a–d).

  11. Describe what happens to each of the following during mitosis and indicate the phase(s) during which each change occurs (VI.A.2.a–d):

    1. Nucleolus

    2. Nuclear envelope

    3. Nuclear lamins

    4. Centrioles

    5. Spindle apparatus

    6. Golgi apparatus

    7. Chromatin

    8. Cytoplasmic microtubules

  12. Give examples of tissues characterized by fast and slow mitotic rates (VI.B.1).

  13. List in order, the phases of interphase (VI.B.1–3; Fig. 3–2) and indicate which is associated with:

    1. Most protein and RNA synthesis

    2. Restoration of cell volume

    3. Exit from the cell cycle and entry into G0

    4. DNA synthesis and replication

    5. Duplication of the centrioles

    6. Accumulating energy (ATP) for mitosis

  14. Diagram the cell-cycle phases (Fig. 3–2). Include molecules that affect transitions from phase to phase at the points in the cycle where they act (VI.B.4 and 5.a–c).

  15. Beginning with transcription, trace the steps in the synthesis and secretion of a glycoprotein and relate the steps to the organelles involved. (This exercise helps to integrate the information in Chapters 2 and 3.)


I. General Features of Nuclei

A. Major Components

Each nucleus has a nuclear envelope, chromatin, one to several nucleoli, and a variable amount ...

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