Ch 9: The Cell Cycle (from Campbell Biology) Flashcards
Animal cytokinesis (does/ does not) involve the fusion of Golgi-derived vesicles.
does not
The cell cycle control system has been compared to the control device of a washing machine (Figure 9.15). Like the washer’s timing device, the cell cycle control system proceeds on its own, according to a built-in clock. However, just as a washer’s cycle is subject to both internal control (such as the sensor that detects when the tub is filled with water) and external adjustment (such as starting the machine), the cell cycle is regulated at certain checkpoints by both _______ and ________ signals.
internal
external
In the middle of the M phase, after prometaphase, the checkpoint M happens. Without full __________ __________ (to the mitotic spindle apparatus), a stop signal is received.
chromosome attachment
Platelet-derived growth factor (PDGF), which is made by blood cell fragments called platelets. The experiment (illustrated in Figure 9.17) demonstrates that PDGF is required for the division of cultured fibroblasts, a type of connective tissue cell. Fibroblasts have PDGF receptors on their plasma membranes. The binding of PDGF molecules to these receptors triggers a signal transduction pathway that allows the cells to pass the G1 checkpoint and divide. PDGF stimulates __________ ________ not only in the artificial conditions of cell culture, but also in an animal’s body. When an injury occurs, platelets release PDGF in the vicinity. The resulting proliferation of fibroblasts helps heal the wound.
fibroblast division
The effect of an external physical factor on cell division is clearly seen in _______-_________ inhibition, a phenomenon in which crowded cells stop dividing.
density-dependent
Cancer cells often don’t follow the “rule” of density-dependent inhibition.
Within the nucleus of a ___________ ____, the DNA is organized into discrete units called chromosomes, structures that carry the genetic information. Each chromosome contains one long DNA molecule associated with many proteins.
non-dividing cell
Microtubules—hollow rods constructed from globular proteins called ________—shape and support the cell and serve as tracks along which organelles equipped with motor proteins can move.
tubulins
Protein phosphorylation causes a _____ ______ in the phosphorylated protein. The shape change results from the interaction of the newly added phosphate groups with charged or polar amino acids on the protein being phosphorylated. The shape change alters the function of the protein, most often activating it, but in some cases phosphorylation instead decreases the activity of the protein.
shape change
A typical human cell has about ___ of DNA – a length about 250,000 times greater than the cell’s diameter.
2 m
Where does the term chromosome come from?
Greek words ‘chroma’ meaning color, and ‘soma’ meaning body. They were named this because they take up certain dyes in microscopy.
Together, the entire complex of DNA and proteins that is the building material of chromosomes is referred to as _______.
chromatin
What is meant by the term “somatic cells” of the human body?
All the body’s cells except for reproductive cells.
All human somatic cells contain __ chromosomes, or two sets of __ chromosomes, one set inherited from each parent.
46
23
The number of chromosomes in somatic cells varies widely across species: __ in cabbage plants, __ in chimpanzees, __ in elephants.
18
48
56
After DNA replication, chromosomes ________ as a part of cell division. Each chromatin fiber becomes densely ______ and folded, making the chromosomes much shorter, and so thick that we can see them with a light microscope.
condense
coiled
Each duplicated chromosome consists of two ______ __________, which are joined copies of the original chromosome.
sister chromatids
The two sister chromatids, each containing an identical DNA molecule, are typically attached all along their lengths by protein complexes called ________; this attachment is known as ______ _________ ________.
cohesins
sister chromatid cohesion
What is the centromere of the sister chromatid?
a region (made up of repetitive sequences) in the chromosomal DNA where the chromatid is most closely attached to its sister chromatid
What are the 3 phases of interphase?
G1 phase (1st gap) S phase (synthesis) G2 phase (2nd gap)
During what phases are the sister chromatids present?
Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.
During what phases is the DNA condensed?
Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.
Does the cell contain twice as much DNA in this phase as it did in the G1 phase?
Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.
Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms.
Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.
These signals report whether crucial cellular processes that should have occurred by that point have in fact been completed correctly and thus whether or not the cell cycle should proceed. Checkpoints also register signals from outside the cell, as we’ll discuss later. (The signals are transmitted within the cell by the kinds of signal transduction pathways discussed in Concept 5.6.) Three important checkpoints are those in the G1, G2, and M phases (red gates in Figure 9.15).
