Chapter 9 The Cell Cycle

Cell division

Reproduction of cells

Cell cycle

The life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells

Genome

The genetic material of an organism or virus; the complete complement of an organism's or virus's genes along with its noncoding nucleic acid sequences

Chromosome

A cellular structure consisting of one DNA molecule and associated protein molecules.

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes.

Somatic cells

All body cells except the reproductive cells in a sexually reproducing organism

Gametes

The reproductive cells of a sexually reproducing organism

Sister chromatids

Two copies of a duplicated chromosome attached to each other by proteins at the centromere and , sometime, along the arms.

Centromere

In a duplicated chromosome, the region on each siser chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences; this close attachment causes a constriction in the condensed chromosome

Mitosis

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase, Chromosome number is conserved by allocating replicated chromosomes equally to each of the daughter nuclei

Cytokinesis

The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II

Mitotic (M) phase

The phase of the cell cycle that includes mitosis and cytokinesis

Interphase

The period in the cell cycle when the cell is not dividing. Cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase; accounts for about 90% of the cell cycle

G1 phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated

G2 phase

The second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs

Prophase

The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact

Prometaphase

The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes

Metaphase

The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.

Anaphase

The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell

Telophase

The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.

Mitotic spindle

An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.

Centrosome

A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles

Aster

A radial array of short microtubules that extends fro each centrosome toward the plasma membrane in an animal cell undergoing mitosis

Kinetochore

A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle

Metaphase plate

An imaginary structure located at a plane midway between the two poles of a cell in metaphase on which the centromeres of all the duplicated chromosomes are located.

Cleavage

The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane

Cleavage furrow

The first sign of cleavage in an animal cell; a shallow groove around the cell in the cell surface near the old metaphase plate

Cell plate

A membrane-bounded, flattened sac located at the midline of a dividing plant cell, inside which the new cell wall forms during cytokinesis

Binary fission

A method of asexual reproduction by 'division in half.' In prokaryotes, this does not involve mitosis, but in single-celled eukaryotes, mitosis is part of the process.

Origin of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

Cell cycle control system

A cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle

Checkpoint

A control point in the cell cycle where stop and go-ahead signals can regulate the cycle

G0 phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly

Growth factor

A protein that must be present in the extracellular environment for the growth and normal development of certain types of cells

Density-dependent inhibition

The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another

Anchorage dependence

The requirement that a cell must be attached to a substratum in order to initiate cell division

Transformation

The conversion of a normal animal cell to a cancerous cell

Benign tumor

A mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin

Malignant tumor

A cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites; can impair the functions of one or more organs

Metastasis

The spread of cancer cells to locations distant from their original site.