AP Biology Unit 9

Cell Cycle

An ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two.

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.

Chromosomes

A cellular structure consisting of one DNA molecule and associated protein molecules. A eukaryotic cell typically has multiple linear ones in the nucleus while a prokaryotic cell typically has one circular one found in the nucleoid.

Cell division

The reproduction of cells.

Chromatin

Complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form as a mass of very long, thin fibers.

Somatic Cells

Any cell in a multicellular organism except a sperm or egg cell or their precursors.

Gametes

A haploid reproductive cell, such as an egg or sperm. They unite during sexual reproduction to produce a diploid zygote.

Sister Chromatids

Two copies of a duplicated chromosome attached to each other by proteins at the centromere and sometimes along the arms. While joined, they make up one chromosome.

Centromere

In a duplicated chromosome, the region on each sister chromatid where they most closely attach 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. Mitosis conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.

Cytokinesis

Division of the cytoplasm forming two 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

A 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. It accounts for about 90% of the cell cycle.

G1 Phase

The first 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 growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

Prophase

The first phase of mitosis in which condenses into discrete chromosomes. The mitotic spindle begins to form and the nucleolus disappears but the nucleus remains intact.

Prometaphase

The second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, 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 the 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. It has two centrioles.

Aster

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell going through mitosis.

Kinetochore

A structure

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

(1) The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. (2) The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.

Cleavage Furrow

The first sign of cleavage in an animal cell; a shallow groove 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, it 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

1) A protein that must be present in the extracellular environment for the growth and development of certain types of cells. 2) A local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.

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

(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, it results in horizontal gene transfer.

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. They can impair the functions of one or more organs.

Metastasis

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