Cell Cycle and Its Regulation

The stage of the cell cycle between cell divisions, which includes the G1, S, and G2 phases. During interphase, the celll grows, replicates its chromosomes, and prepares for mitosis

The stage of the cell cycle in which replicated chromosomes are separated into 2 new nuclei. Mitosis consists of prophase, metaphase, anaphase, and telophase

The division of the cytoplasm at the end of mitosis or meiosis. In cells without a cell wall, a cleavage furrow forms to divide the cytoplasm. In cells with a cell wall, a cell plate is formed, as well as a cleavage furrow

A growth phase during interphase of the cell cycle, during which the cell grows and cellular organelles are replicated. G1 precedes the S phase

The phase of interphase in which the DNA is replicated. At the end of the S phase, a cell contains twice the amount of DNA that is had at the beginning of the S phase. The S phase follows G1 and proceeds G2

The phase of interphase following the S phase, during which the cell continues to grow and prepare for mitoses

The phase of mitosis during which chromatin condenses into visible chromosomes and the spindle fibers form in the nucleus. Prophase follows interphase and precedes metaphase

The phase of mitosis during which the chromosomes align along the center of the cell (also known as the metaphase plate). Metaphase follows prophase and precedes anaphase

The phase of mitosis during which the centromeres of the chromosomes split and the two chromatids separate and begin to move to opposite sides of the cell. At this point, each chromatid has its own centromere and is considered a separate chromosome. Anaphase follows metaphase and precedes telophase

The phase during which 2 new nuclei are formed. Telophase follows anaphase and usually precedes cytokinesis

The phase of the cell cycle during which a cell is not actively dividing. Fully differentiated cells are in G0. Cellular signals may cause a cell to either enter or leave G0 depending on cellular conditions

Checkpoints regulate the progression of the cell cycle. Checkpoints occur at multiple points in the cell cycle and can stop the cell cycle if defects in components necessary for cell division are detected. Checkpoints may prevent mutated cells from dividing and causing tumors

Proteins whose levels vary throughout the cell cycle. Cyclins bind with cyclin-dependent kinases to form mitosis promoting factor (MPF). When levels of MPF are high enough, a cell will enter mitosis

Proteins which, when bonded to cyclins, form mitosis-promoting factor (MPF). When levels of MPF are high enough, a cell will enter mitosis. Levels of cyclin-dependent kinases are relatively constant during the cell cycle

Mitosis-promoting factor. This is a complex of cyclin-dependent kinases bound to cyclin proteins. High levels of mitosis-promoting factor will signal a cell to start mitosis

The process in normally dividing cells in which cells that exceed a particular density stop dividing. Density-dependent inhibition stops uncontrolled cell division. Malignant cells do not exhibit density-dependent inhibition

In some cell types, cells must be attached to a surface to continue dividing. Malignant cells do not exhibit anchorage dependence

Genes that stimulate normal rates of cell division. If a proto-oncogene is mutated, it may become an oncogene, which stimulates excessive rates of cell division. Proto-oncogenes are analogous to the accelerator on a car between they stimulate cell division

cancer-causing genes that stimulate excessive rates of cell division

Genes that detect defects in DNA replication and will stop the cell cycle if mutations are detected. Tumor suppressor genes are analogous to the brakes on a car because they stop cell division from proceeding

Programmed cell death. Apoptosis may occur if mutations are detected in a cell. Apoptosis also occurs during development. For example, in embryonic development, fingers are initially connected by a weblike structure: at the appropriate time in development, apoptosis eliminates thus weblike structure, resulting in serparated fingers

(A) G0 is the stage of the cell cycle in which the cell is not actively dividing. Fully differentiated cells are in G0. Interphase consists of G1, S, and G2, so choices (B), (C), and (D) are incorrect

Tumor suppressor genes detect in DNA replication and prevent the replication of cells with those defects. Choice (A) is incorrect because cyclin-dependent kinases are not involved in detecting mutations. Both oncogenes and proto-oncogenes stimulate cell division so choices (B) and (C) are incorrect

(C) if positive feedback occurs, a stimulus increases the strength of a response and moves the system further from homeostasis, which is the case with oxytocin and uterine contractions. Choices (A), (B), and (D) are incorrect because they describe negative feedback, which brings a system closer to homeostasis