Biology Chapter 8

Front 1

Life Cycle

Back 1

The entire sequence of stages in the life of an organism, from the adults of the next.

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Genome

Back 2

A complete (haploid) set of an organism's genes; an organism's genetic material.

Front 3

Asexual reproduction

Back 3

The creation of offspring by a single parent, without the participation of sperm and egg.

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Chromosome

Back 4

A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Chromosomes consist of a chromatin, a combination of DNA and protein.

Front 5

Sexual Reproduction

Back 5

The creation of offspring by the fusion two haploid sex cells (gametes), forming a diploid zygote.

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Cell Division

Back 6

The reproduction of a cell.

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Binary Fission

Back 7

A means of asexual reproduction in which a parent organism, often a single cell, divides into two individuals of about equal size.

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Chromatin

Back 8

The complex of DNA and proteins that constitues eukaryotic chromosomes; often useed to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.

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Sister Chromatid

Back 9

One of the two identical parts of a duplicated chromosome in a eukaryotic cell.

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Centromere

Back 10

The region of a duplicated chromosome where two sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis. The centromere divides at the onset of anaphase during mitosis anaphase II during meiosis.

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Cell Cycle

Back 11

An ordered sequence of events (including interphase and the mitotic phase) that extends from the time a eukaryotic cell is first formed from a dividing parent cell until its own division into two cells.

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Interphase

Back 12

The period in a eukaryotic cell cycle when the cell is not actually diving. Interphase constitutes the majority of the time spent in the cell cycle.

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Mitotic Phase (M Phase)

Back 13

The part of the cell cycle when the nucleus is divided (via mitosis), its chromosomes are distributed to the daughter nuclei, and the cytoplasm divided (via cytokinesis), producing two daughter cells.

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Cytokinesis

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The division of the cytoplasm to form two seperate daughter cells. Cytokinesis usually occurs during telophase of mitosis. Mitosis and cytokinesis make up the mitotic (M) phase of the cell cycle.

Front 15

Prophase

Back 15

The first stage of mitosis, during which the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still intact.

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Prometaphase

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The second stage of mitosis, during which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids.

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Metaphase

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The third stage of mitosis, during which all the cell's duplicated chromosomes are lined up at an imaginary plane euqidistant between the poles of the mitotic spindles.

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Anaphase

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The fourth stage of mitosis, beginning when sister chromatids speperate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell.

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Telophase

Back 19

The fifth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. Telophase usually occurs together with cytokinesis.

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Centrosome

Back 20

Material in the cytoplasm of a eukaryotic cell that gives rise to microtubules; important in mitosis and meiosis; also called microtube-organizing center.

Front 21

Cleavage Furrow

Back 21

The first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphase plate.

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Growth Factor

Back 22

A protein secreted by certain body cells that stimulates other cells to divide.

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Density-dependent Inhibition

Back 23

The arrest of cell division that occurs when cells grown in a laboratory dish touch one another.

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Anchorage Dependence

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The requirement that to divide, a cell must be attached to a solid surface.

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Cell Plate

Back 25

A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.

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Cell Cycle Control System

Back 26

A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle.

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Tumor

Back 27

An abnormal mass of cells that forms within otherwise normal tissue.

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Benign Tumor

Back 28

An abnormal mass of cells that remains at its original site in the body.

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Malignant Tumor

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

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Metastasis

Back 30

The spread of cancer cells beyond their original site.

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Carcinoma

Back 31

Cancer that originates in the coverings of the body, such as skin or lining of the intestinal tract.

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Sarcoma

Back 32

Cancer of the supportive tissues, such as bones, cartilage, and muscle.

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Leukemia

Back 33

A type of cancer of the blood-forming tissues, characterized by an excessive production of white blood cells and abnormally high number of them in the blood; cancer of the bone marrow cells that produce leukocytes.

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Lymphoma

Back 34

Cancer of the tissues that form white blood cells.

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Somatic Cell

Back 35

Any cell in a multicellular organism exceot a sperm or egg cell or a cell that develops into a sperm or egg.

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Homologous Chromosomes

Back 36

The two chromosomes that make up a matched pair in a diploid cell. Homologous chromosomes are of the same length, centromere position, and stainin pattern and posses genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother.

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Locus (Plural loci)

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The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding gene loci.

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Diploid Cell

Back 38

In an organism that reproduces sexually, a cell containing two homologous sets of chromosomes, one set inherited from each parent; a 2n cell.

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Sex Chromosome

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A chromosome that determines whether an individual is male or female.

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Autosome

Back 40

A chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X and Y.

Front 41

Gamete

Back 41

A sex cell; a haploid egg or sperm. The union of two gametes of opposite sex (fertilization) produces a zygote.

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Haploid Cell

Back 42

In the life cycle of an organism that reproduces sexually, a cell containing a single set of chromosomes; an n cell.

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Fertilization

Back 43

The union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote.

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Zygote

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The fertilized egg, which is diploid, that results from the union of a sperm cell nucleus and an egg cell nucleus.

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Tetrad

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A paired set of homologous chromosomes, each composed of two sister chromatids. Tetrads form during prophase I of meiosis.

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Crossing Over

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The exchange of segments between chromatids of homologous chromosomes during synapsis in propahse I of meiosis; also, the exchange of segments between DNA molecules in prokaryotes.

Front 47

Chiasma

Back 47

The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis.

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Genetic Recombination

Back 48

The production, by crossing over and/or independent assortment of chromosomes during meiosis, of offspring with allele combinations different from those in the parents. The term may also be used more specifically to mean the production by crossing over of eukaryotic of prokaryotic chromosomes with gene combinations different from those in the original chromosomes.

Front 49

Karyotype

Back 49

A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position.

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Trisomy 21 (Down Syndrome)

Back 50

A human genetic disorder resulting from the presence of an extra chromosome 21; characterized by heart and respiratory defects and varying degrees of mental retardation.

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Nondisjunction

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An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase.

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Deletion

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The loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome.

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Duplication

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Repetition of part of a chromosome resulting from fussion with a fragment from a homologous chromosome; can result from an error in meiosis or from mutagenesis.

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Inversion

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A change in a chromosome resulting from reattachment of a chromosome fragment to the original chromosome, but in a reverse direction. Mutagens and errors during meiosis can cause inversions.

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Translocation

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(1) During protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to the P site on a ribosome. (The mRNA travels with it.) (2) A change in a chromosome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis.