Campbell Biology Chapter 12

cell division

the process in reproduction and growth by which a cell divides to form daughter cells

cell cycle

series of events in which a cell grows, prepares for division, and divides to form two daughter cells

genome

all the DNA in one cell of an organism

chromosome

a threadlike body in the cell nucleus that carries the genes in a linear order

chromatin

the substance that composes eukaryotic chromosomes; it consists of specific proteins, DNA, and small amounts of RNA

somatic cell

cell that makes up all of the body tissues and organs, except gametes

gametes

reproductive cells, sperm cells and egg cells

sister chromatids

Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.

centromere

a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape

mitosis

part of eukaryotic cell division during which the cell nucleus divides

cytokinesis

division of the cytoplasm during cell division

Walther Flemming

German scientist who in 1882 developed dyes that allowed him to observe the behavior of chromosomes during mitosis and cytokinesis,

M phase

the phase in the cell cycle where mitosis and cytokinesis occur resulting in cell division, the shortest part of cell cycle

interphase

the period of the cell cycle during which activities such as cell growth and protein synthesis occur without visible signs of cell division - about 90% of 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

stage of interphase in which cell duplicates its cytosol and organelles

prophase

first and longest phase of mitosis in which the genetic material inside the nucleus condenses and the chromosomes become visible

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 stage in mitosis or meiosis in which the duplicated chromosomes line up along the equatorial plate of the spindle

anaphase

phase of mitosis in which the chromosomes separate and move to opposite ends of the cell

telophase

last phase of mitosis, chromosome are in two new cells and nuclear membranes start to reform

mitotic spindle

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

centrosome

Central microtubule organizing center of cells. In animal cells, it contains two centrioles, which are not essential for cell division.

aster

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

kinetochore

a structure of proteins associated with specific sections of chromosomal DNA at each centromere

metaphase plate

An imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles

separase

-This is the enzyme that breaks down cohesion so that the chromatids can separate.

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 in the cell surface near the old metaphase plate.

cell plate

the precursor of a new plant cell wall that forms during cell division and divides a cell into two

binary fission

the division of a prokaryotic cell into two offspring cells

origin of replication

Site where the replication of a DNA molecule begins

cell cycle control system

A cyclically operating set of molecules in the cell that 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.

3 major checkpoints

G1, G2, M

G1 checkpoint

"restriction point", if a cell receives a go-ahead signal at the checkpoint, it will complete the G1,S,G2, and M phases and divide, if it does not receive a go-ahead signal at that point, it will exit the cycle, switching into the G0 phase

G0 phase

a phase of the cell cycle in which the cell is not dividing and its DNA is not replicating

cyclin

A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle.

cyclin-dependent kinases

a kinase that in order to drive the cell cycle must be attatched to a cycln to become active

MPF

Maturation-promoting factor (M-phase-promoting factor); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.

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 to divide, a cell must be attached to the substratum.

transformation

The conversion of a normal animal cell to a cancerous cell.

benign tumor

A mass of abnormal cells that remains at the site of origin.

malignant tumor

an abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor

metastasis

spread of cancer cells beyond their original site in the body