Chapter 12 Homework

Which of these phases encompasses all of the stages of mitosis but no other events? A B C E D

During _____ both the contents of the nucleus and the cytoplasm are divided. During _____ both the contents of the nucleus and the cytoplasm are divided. S G1 mitosis G2 the mitotic phase

During _____ the cell grows and replicates both its organelles and its chromosomes. During _____ the cell grows and replicates both its organelles and its chromosomes. S G1 mitosis cytokinesis interphase

In eukaryotic cells, chromosomes are composed of _____. In eukaryotic cells, chromosomes are composed of _____. DNA and RNA DNA only DNA and proteins DNA and phospholipids

Nucleoli are present during _____. Nucleoli are present during _____. prophase interphase metaphase anaphase prometaphase

Cytokinesis often, but not always, accompanies _____. Cytokinesis often, but not always, accompanies _____. telophase prometaphase anaphase metaphase interphase

Chromosomes become visible during _____. Chromosomes become visible during _____. prophase anaphase metaphase interphase prometaphase

Centromeres divide and sister chromatids become full-fledged chromosomes during _____. Centromeres divide and sister chromatids become full-fledged chromosomes during _____. telophase anaphase prometaphase metaphase interphase

Spindle fibers attach to kinetochores during _____. Spindle fibers attach to kinetochores during _____. metaphase telophase interphase prometaphase anaphase

Anaphase

Cytokinesis as it occurs in animal cells

Prophase

Metaphase

Prometaphase

Cytokinesis as it occurs in plant cells

Telophase

Some cells have several nuclei per cell. How could such multinucleated cells be explained? Some cells have several nuclei per cell. How could such multinucleated cells be explained? The cell underwent repeated mitosis, but cytokinesis did not occur. The cell underwent repeated cytokinesis but no mitosis. The cell had multiple S phases before it entered mitosis. The cell underwent repeated mitosis with simultaneous cytokinesis.

During which phase of mitosis do the chromatids become chromosomes? During which phase of mitosis do the chromatids become chromosomes? prophase anaphase cytokinesis metaphase telophase

The first gap in the cell cycle (G1) corresponds to _____. The first gap in the cell cycle (G1) corresponds to _____. the phase between DNA replication and the M phase the phase in which DNA is being replicated the beginning of mitosis normal growth and cell function

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2? A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2? 8; 16 8; 8 12; 16 16; 8 16; 16

A cell in late anaphase of mitosis will have _____. A cell in late anaphase of mitosis will have _____. one large nuclear envelope no chromosomes in the center of the cell chromosomes clustered tightly at the center chromosomes clustered at one end of the cell individual chromatids beginning to separate from one another

What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2? What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2? Nothing happens. The cells enter mitosis. The cells undergo meiosis. Cell differentiation is triggered.

The decline of MPF activity at the end of mitosis is due to _____. The decline of MPF activity at the end of mitosis is due to _____. the accumulation of cyclin synthesis of DNA the degradation of cyclin decreased synthesis of Cdk the destruction of the protein kinase Cdk

For the cell, why is it better to be held in G1 rather than S, G2, or M phase? For the cell, why is it better to be held in rather than , , or phase? G1 cells are the only ones that do not have their chromatin in a highly condensed state. MPF is required to enter S phase, so the cell is committed to entering M phase if the cycle moves beyond G1. G1 cells have not replicated their DNA in preparation for division. G1 cells are larger and more likely to perform the normal functions of the cell.

What would happen if the kinase that adds the inhibitory phosphate to Cdk were defective? What would happen if the kinase that adds the inhibitory phosphate to Cdk were defective? MPF levels would become abnormally high. M phase would begin prematurely. The onset of M phase would be delayed. Cdk concentrations would spike.

What role(s) do gap phases play in the cell cycle? What role(s) do gap phases play in the cell cycle? They allow chromosome replication to occur. They allow chromosomes to condense prior to mitosis. They allow cells to replicate organelles and manufacture additional cytoplasm. They allow the nuclear envelope to re-form after mitosis.