Ch. 12 Guided Reading Version PDF

Preview

Summary

Notes from lecture ...

Description

Adapted from L. Miriello by S. Sharp

Name: Chapter 12 Guided Reading Assignment

1. Compare and contrast the role of cell division in unicellular and multicellular organisms. In unicellular organisms cell division is a process of asexual reproduction. In multicellular organisms the division of all cells, other than the reproductive cells, is known as mitosis. 2. Define the following terms: a. Genome: Cell’s genetic information- DNA. b. Chromosomes: structures that package DNA molecules. c. Chromatin: Entire complex of DNA and proteins that is the building material of chromosomes. d. Somatic cells: All body cells, except the reproductive cells. Each contain 46 chromosomes, two sets of 23; one inherited from each parent. e. Gametes: reproductive cells; sperm and eggs. They have one set, 23, chromosomes. f. Sister chromatids: Joined copies of the original chromosome, which each contain an identical DNA molecule, and are initially attached all along their lengths by protein complexes called cohesins. g. Centromere: A region in each sister chromatid containing specific DNA sequences where the chromatid is attached most closely to its sister chromatid. h. Mitosis: The division of genetic material in the nucleus. i. Cytokinesis: The division of the cytoplasm. j. Meiosis: Production of gametes. Yields non-identical daughter cells that have only one set of chromosomes. It occurs in the gonads, ovaries or testes, and reduces the chromosome number from 46 to 23.

Page 1 of 6

Adapted from L. Miriello by S. Sharp

3. List the activities of the cell cycle: a. Mitotic (M) phase: Shortest part of the cycle that includes both mitosis and cytokinesis. The phase in the cycle when the cell divides. b. Interphase: Alternates with Mitotic cell division. It is a longer phase that accounts for 90% of the cycle, where a cell that is about to divide, grows and copies its chromosomes in preparation for cell division. c. G1 phase: A subphase of interphase, the first gap. This is the subphase where a cell grows.

d. S phase: A second subphase of interphase, synthesis. Chromosomes are only duplicated during this phase. During this phase the cell continues to grow as it copies its chromosomes.

e. G2 phase: A third subphase of interphase, the second gap. During this phase the cell grows more as it completes preparations for cell division. During all three subphases, a cell that will eventually divide grows by producing proteins and cytoplasmic organelles such as the mitochondria and the endoplasmic reticulum. The daughter cells then repeat this cycle.

Page 2 of 6

Adapted from L. Miriello by S. Sharp

Label the diagram below:

G2 of Interphase

Metaphase

Prophase

Anaphase

Page 3 of 6

Prometaphase

Telophase and Cytokinesis

Adapted from L. Miriello by S. Sharp

4. Contrast cytokinesis in plant and animal cells. In animal cells cytokinesis occurs by cleavage, while in plant cells there is no cleavage furrow and instead during telophase vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell where they coalesce and produce a cell plate. 5. Define binary fission and label the diagram below: Binary Fission: is the process of a cell undergoing a type of reproduction where it grows twice its size and then divides to form two cells. It also refers to asexual reproduction of eukaryotic cells.

Bacterial Cell Division by Binary Fission Chromosome replication begins. One copy of the origin moves toward the other end of the cell.

Replication continues. One copy of the origin is now at each end of the cell, while the cell elongates.

Replication finishes. The plasma membrane grows inward and a new cell wall is deposited.

Two Daughter cells result.

6. Discuss the hypothetical evolution of mitosis. Mitosis evolved from simpler prokaryotic mechanisms of cellular reproduction. 7. What is the cell cycle control system and how do checkpoints play into this? The cell cycle control system is a cyclically operating set of molecules in the cell that both triggers and coordinates key events. A checkpoint is a control point where stop and go-ahead signals regulate the cycle and are transmitted through within the cell.

Page 4 of 6

Adapted from L. Miriello by S. Sharp

8. What is a cyclin and what does it activate? It is a protein that cyclically fluctuates concentration in the cell. It controls the progression of cells through the cell cycle by activating cyclin- dependent kinase enzymes. 9. What are Cdk’s? Cyclin-dependent Kinases 10. What does MPF stand for and what does it promote? Maturation-promoting factor, and it triggers the cell’s passage past the G2 checkpoint into M phase. It causes phosphorylation of various proteins of the nuclear lamina, which promotes fragmentation of the nuclear envelope during prometaphase of mitosis. 11. Label the diagram below illustrating the molecular control of the cell cycle. Fluctuation of MPF activity and cyclin concentration during the cell cycle. This illustrates the process below and the MPF activity (purple) and the cyclin concentration (red) in relation to time during the cycle. The control of the cell cycle of molecular mechanisms that help regulate the cycle.

Page 5 of 6

Adapted from L. Miriello by S. Sharp

12. What is a growth factor? A protein released by certain cells that stimulates other cells to divide. 13. What is density-dependent inhibition? A phenomenon in which crowded cells stop dividing. The effect of an external physical factor on cell division is seen in this. 14. What is anchorage dependence? Exhibited in most animal cells, where in order to divide they must be attached to a substratum, such as the extracellular matrix of a tissue. 15. Define the following terms: a. Transformation: The process that coverts a normal cell into a cancer cell. b. Benign tumor: Abnormal cells that remain at the original site if they have too few genetic and cellular changes to survive at another site. c. Malignant tumor: Includes cells whose genetic and cellular changes enable them to spread to new tissues and impair the functions of one or more organs. d. Metastasis: The spread of cancer cells to locations distant from their original site. An individual with a malignant tumor is said to have cancer.

Page 6 of 6...