Chapter 12

Anaphase

third phase of mitosis, during which disjunction occurs and the spindle apparatus begins moving separated chromosomes toward the cellular poles.

Cell cycle

a recurring, repeated series of events that begins when a cell is formed through cell division and ends when that cell divides; in other words, the life cycle of a cell. The cell cycle of most haploid cells consists of interphase, mitosis, and cytokinesis

Cell plate

structure which appears between the two new nuclei during cytokinesis in plants and fungi. The cell plate forms from vesicles containing cellulose (in plants) or chitin (in fungi), and becomes the cell wall dividing the two new daughter cells.

Centriole

paired barrel-shaped structures from which the spindle apparatus grows during prophase.

Centromere

location on a replicated chromosome where the two chromatids are joined together; this is also the point where the spindle apparatus attaches during mitosis or meiosis.

Chromatid

one half of a replicated chromosome, before disjunction occurs.

Chromosome

a single DNA molecule and its associated histone proteins.

Cleavage furrow

groove that forms around the equator of the parent cell during cytokinesis in animal cells. The furrow is caused by a ring of microtubules which contract in on themselves, squeezing the parent cell into two daughter cells.

Cytokinesis (cytoplasmic division)

last portion of the cell cycle, during which the parent cell divides into two daughter cells.

Diploid

refers to cells which have two copies of each of their chromosomes. Most somatic cells in humans and other animals are diploid.

G1

first portion of interphase. The "G" stands for growth. This is the portion of the cell cycle during which the cell does the job it is made to do. For instance, if it is a gland cell, this is when the cell makes its product.

G2

third portion of interphase. This is the portion of interphase during which cell builds cellular components so that it may begin the process of cell division.

Germ cell

cells in the gonads which make gametes.

Haploid

refers to cells which have only one copy of each chromosome. In humans and other animals, these cells are usually certain germ cells and all gametes.

Histone

protein molecules which act as spools around which DNA winds, and which also have a role in gene regulation.

Interphase

portion of the cell cycle during which the cell spends most of its life. Interphase consists of three portions: G1, S, and G2.

Meiosis

portion of the cell cycle in gamete formation during which the diploid number of chromosomes is halved, resulting in haploid gametes.

Metaphase

second phase of mitosis, during which chromosomes are lined up at the cellular equator.

Mitosis

portion of the cell cycle in diploid cells in which chromosome pairs are separated and sorted out to daughter cells.

Nucleosome

structure formed by a DNA molecule winding around 8 histone molecules. Nucleosomes give a DNA molecule an appearance of "beads on a string" when viewed under an electron microscope.

Prophase

first phase of mitosis. During prophase, the spindle apparatus forms, the nuclear membrane breaks up into vesicles which move to the sides of the cell, and chromosomes condense and become visible under a light microscope, and then are moved by the spindle

S

second portion of interphase. The "S" stands for "synthesis." This is the portion of interphase during which DNA is replicated so that cell division may begin.

Somatic cell

any cell of the body, not including germ cells or gametes.

Spindle apparatus (also called mitotic spindle or mitotic apparatus)

a temporary part of the cytoskeleton which forms during prophase. The spindle apparatus attaches to the chromosomes at the centromere and pulls them to the cellular equator, then to opposite poles of the cell after disjunction.

Telophase

fourth phase of mitosis, during which the separated chromosomes have been pulled by the spindle apparatus to opposite poles of the cell, and the nuclear membrane begins reforming around the two sets of chromosomes.

Anaphase

third phase of mitosis, during which disjunction occurs and the spindle apparatus begins moving separated chromosomes toward the cellular poles.

Cell cycle

a recurring, repeated series of events that begins when a cell is formed through cell division and ends when that cell divides; in other words, the life cycle of a cell. The cell cycle of most haploid cells consists of interphase, mitosis, and cytokinesis

Cell plate

structure which appears between the two new nuclei during cytokinesis in plants and fungi. The cell plate forms from vesicles containing cellulose (in plants) or chitin (in fungi), and becomes the cell wall dividing the two new daughter cells.

Centriole

paired barrel-shaped structures from which the spindle apparatus grows during prophase.

Centromere

location on a replicated chromosome where the two chromatids are joined together; this is also the point where the spindle apparatus attaches during mitosis or meiosis.

Chromatid

one half of a replicated chromosome, before disjunction occurs.

Chromosome

a single DNA molecule and its associated histone proteins.

Cleavage furrow

groove that forms around the equator of the parent cell during cytokinesis in animal cells. The furrow is caused by a ring of microtubules which contract in on themselves, squeezing the parent cell into two daughter cells.

Cytokinesis (cytoplasmic division)

last portion of the cell cycle, during which the parent cell divides into two daughter cells.

Diploid

refers to cells which have two copies of each of their chromosomes. Most somatic cells in humans and other animals are diploid.

G1

first portion of interphase. The "G" stands for growth. This is the portion of the cell cycle during which the cell does the job it is made to do. For instance, if it is a gland cell, this is when the cell makes its product.

G2

third portion of interphase. This is the portion of interphase during which cell builds cellular components so that it may begin the process of cell division.

Germ cell

cells in the gonads which make gametes.

Haploid

refers to cells which have only one copy of each chromosome. In humans and other animals, these cells are usually certain germ cells and all gametes.

Histone

protein molecules which act as spools around which DNA winds, and which also have a role in gene regulation.

Interphase

portion of the cell cycle during which the cell spends most of its life. Interphase consists of three portions: G1, S, and G2.

Meiosis

portion of the cell cycle in gamete formation during which the diploid number of chromosomes is halved, resulting in haploid gametes.

Metaphase

second phase of mitosis, during which chromosomes are lined up at the cellular equator.

Mitosis

portion of the cell cycle in diploid cells in which chromosome pairs are separated and sorted out to daughter cells.

Nucleosome

structure formed by a DNA molecule winding around 8 histone molecules. Nucleosomes give a DNA molecule an appearance of "beads on a string" when viewed under an electron microscope.

Prophase

first phase of mitosis. During prophase, the spindle apparatus forms, the nuclear membrane breaks up into vesicles which move to the sides of the cell, and chromosomes condense and become visible under a light microscope, and then are moved by the spindle

S

second portion of interphase. The "S" stands for "synthesis." This is the portion of interphase during which DNA is replicated so that cell division may begin.

Somatic cell

any cell of the body, not including germ cells or gametes.

Spindle apparatus (also called mitotic spindle or mitotic apparatus)

a temporary part of the cytoskeleton which forms during prophase. The spindle apparatus attaches to the chromosomes at the centromere and pulls them to the cellular equator, then to opposite poles of the cell after disjunction.

Telophase

fourth phase of mitosis, during which the separated chromosomes have been pulled by the spindle apparatus to opposite poles of the cell, and the nuclear membrane begins reforming around the two sets of chromosomes.