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Flashcards in Chapter 12 Deck (13)
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1

Increases in the enzymatic activity of some protein kinases important for the regulation of the cell cycle are due to

A) kinase synthesis by ribosomes

B) activation of inactive kinases by binding to cyclins

C) conversion of inactive cyclins to active kinases by means of phosphorylation

D) cleavage of the inactive kinase molecules by cytoplasmic proteases

E) a decline in external growth factors to a concentration below the inhibitory threshold

B) activation of inactive kinases by binding to cyclins

2

Through a microscope, you can see a cell plate beginning to form across the middle of the cell and nuclei reforming on either side of the cell plate. This cell is most likely

A) animal cell during cytokinesis

B) plant cell during cytokinesis

C) animal cell in the S phase

D) a bacterial cell dividing

E) plant cell in metaphase

B) plant cell, cytokinesis

3

Vinblastine us a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of micro-tubules, its effectiveness must be related to

A) disruption of mitotic spindle formation

B) inhibition of regulatory protein phosphorylation

C) suppression of cyclin production

D) myosin denaturation and inhibition of cleavage furrow formation

E) inhibition of DNA synthesis

A) disruption of mitotic spindle formation

4

A particular cell has half as much DNA as some other cells in a mitotic-ally active tissue. The cell in question is most likely in

A) G1

B) G2

C) pro-phase

D) meta-phase

E) ana-phase

A) G1

5

The decline in MPF activity at the end of mitosis is caused by

A) the destruction of the protein kinase(CdK)

B) decreased synthesis of cyclin

C) the degradation of cyclin

D) synthesis of DNA

E) an increase in the cell's volume to genome ratio

C) the degradation of cyclin

6

A red blood cell(RBC) has a life span of 120 days. If an average adult has 5L of blood and each micro-liter contains 5 million RBCs, how many new cells must be produced each SECOND to replace the entire RBC population?

C) 2,400,000

7

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B?

A) spindle formation

B) spindle attachment to kinetochores

C) DNA synthesis

D) cell elongation during anaphase

E) cleavage furrow formation

E) cleavage furrow formation

8

In some organisms, mitosis occurs without cytokinesis occurring. This will result in

A) cells with more than one nucleus

B) cells that are unusually small

C) cells lacking nuclei

D) destruction of chromosomes

E) cell cycles lacking an S phase

A) cells with more than one nucleus

9

1. Describe the structural organization of the genome.

The genome is the genetic information inside the cell, the DNA. In prokaryotic cells, the genome is organized in one long strand that is coiled within the cell. In eukaryotic cells, the genome is packaged into chromosomes in a double helix shape. The chromosomes are made out of a complex of DNA and proteins, or chromatin. Each chromosome has two sister chromatids, each of which contain identical DNA molecules and are attached in the center by a specialized region called the centromere.

10

2. Overview the major events of cell division that enable the genome of one cell to be passed on to two daughter cells.

The major events of cell division that enable the genome of one cell to be passed on to two daughter cells are the S phase, the G2 phase, and the M phase. In the S phase, the DNA is replicated. In the G2 phase, the copied strands are checked for errors. Finally, in the mitosis, both sides of the cell are given a copy of the genome.

11

4. List the phases of the cell cycle and describe the sequence of events that occurs during each phase.

The phases of the cell cycle are interphase and mitosis. Interphase takes up most of the cell’s life, and consists of the G1, S, and G2 phases. In the G1 phase, cells just grow. In the S phase, DNA is replicated to ensure that both new cells will get a complete and identical genome. In the G2 phase, extra organelles are made. The second part of the cell cycle, mitosis, is the shortest phase. In mitosis, the nucleus and DNA split and are sent to opposite sides of the cell. Then finally in cytokinesis, the cytoplasm separates, and two new cells are made.

12

5. List the phases of mitosis and describe the events characteristic of each phase.

The phases of mitosis are prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis. In prophase, the chromatin fibers in the nucleolus begin to coil more tightly into chromosomes and the nucleoli disappear. During this time, the mitotic spindle forms and the centrosomes move away from one another by the microtubules between them. In prometaphase, the nuclear envelope dissolves and the spindle interact with the chromosomes. Kinetochore microtubules take hold of the sister chromatids, whereas nonkinetochore microtubules interact with chromosomes from the opposite pole of the spindle.

13

6. Recognize the phases of mitosis from diagrams or micrographs -- describe the phases using words to describe the pictures. (example = it looks like x's lined up in the middle of the cell...)


 

In G2 of interphase, the genetic information is kept in the nucleolus and is not neatly arranged. Later, during prophase of mitosis, the chromatin become more tightly packed, and look like wiggly x shapes. The centrosomes have stringy objects coming out of them, and are on opposite sides of the cell. In prometaphase, the nucleolus has started to fade, and the fibers that came from the centrosomes get closer to the chromosomes(the x’s). Then, in metaphase, the strings attack to the center of the x’s. The cell begins to stretch out from the force of the strings pushing the cell from the inside out. Anaphase is when the x’s are pulled apart, becoming v’s that move away from each other to the opposite sides of the cell. Telophase is when the spindle begins to retract and there are two nucleoli on each side of the peanut shaped cell. Finally, the cell pinches inward and separates. Now there are two identical twin daughter cells.