3 major checkpoints G1, G2, M Anaphase phase of mitosis in which the chromosomes separate and move to opposite ends of the cell Anchorage dependence The requirement that to divide, a cell must be attached to the substratum. Aster A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis. benign tumor A mass of abnormal cells that remains at the site of origin. binary fission the division of a prokaryotic cell into two offspring cells cell cycle series of events in which a cell grows, prepares for division, and divides to form two daughter cells cell cycle control system A cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle.

cell division the process in reproduction and growth by which a cell divides to form daughter cells cell plate the precursor of a new plant cell wall that forms during cell division and divides a cell into two centromere a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape centrosome Central microtubule organizing center of cells. In animal cells, it contains two centrioles, which are not essential for cell division. Checkpoint A control point in the cell cycle where stop and go-ahead signals can regulate the cycle. Chromatin the substance that composes eukaryotic chromosomes; it consists of specific proteins, DNA, and small amounts of RNA Chromosome a threadlike body in the cell nucleus that carries the genes in a linear order 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. 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 attached to a cyclin to become active cytokinesis division of the cytoplasm during cell division density-dependent inhibition The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another. G0 phase a phase of the cell cycle in which the cell is not dividing and its DNA is not replicating 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 G1 phase The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins. G2 phase stage of interphase in which cell duplicates its cytosol and organelles Gametes reproductive cells, sperm cells and egg cells genome all the DNA in one cell of an organism growth factor a protein that must be present in the extracellular environment for the growth and normal development of certain types of cells 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

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

malignant tumor an abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor metaphase the stage in mitosis or meiosis in which the duplicated chromosomes line up along the equatorial plate of the spindle metaphase plate An imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles metastasis spread of cancer cells beyond their original site in the body mitosis part of eukaryotic cell division during which the cell nucleus divides mitotic spindle An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis. 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. M phase the phase in the cell cycle where mitosis and cytokinesis occur resulting in cell division, the shortest part of cell cycle origin of replication Site where the replication of a DNA molecule begins 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. Prophase first and longest phase of mitosis in which the genetic material inside the nucleus condenses and the chromosomes become visible Separase -This is the enzyme that breaks down cohesion so that the chromatids can separate. sister chromatids Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II. somatic cell cell that makes up all of the body tissues and organs, except gametes S phase The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated. Telophase last phase of mitosis, chromosome are in two new cells and nuclear membranes start to reform transformation The conversion of a normal animal cell to a cancerous cell.

signal transduction pathway the process by which a signal on a cell’s surface is converted into a specific cellular response biofilm A microbial community that usually forms as a slimy layer on a surface local regulators Messenger molecules secreted by the signaling cell which only travel short distance and influence cells in the local vicinity growth factor one of a group of external regulatory proteins that stimulate the growth and division of cells paracrine signaling a type of local signaling where the target cell is close to the signal-releasing cell synaptic signaling a type of local signaling specific to neurotransmitters in nerve cells hormones

chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another long-distance signaling cell is secreting a hormone and the hormone must travel through the blood stream to reach its target place. 3 stages of cell signaling 1. Reception 2. Transduction 3. response

reception the target cell’s detection of a signal molecule coming from outside the cell transduction in cellular communication, the conversion of a signal from outside the cell to a form that can bring about a specific cellular response signal transduction pathway A series of steps linking a mechanical or chemical stimulus to a specific cellular response. relay molecule molecule in a signal transduction pathway response In cellular ommunication, the change in a specific cellular activity brought about by a transduced signal from outside the cell. Ligand A molecule that binds specifically to a receptor site of another molecule. G-protein coupled receptor A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein. G-protein A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell. receptor tyrosine kinases

belong to a major class of plasma membrane receptors characterized by having enzymatic activity – attach phosphates to tyrosine’s dimer a compound whose molecules are composed of two identical monomers

ligand-gated ion channel a type of membrane receptor containing a region that can act as a “gate” when the receptor changes shape intracellular receptor describes a receptor that binds to its signal inside the cell, must be nonpolar (testosterone acts as transcription factor) protein kinase An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein. protein phosphatase An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.

second messenger A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein. cAMP

is a second messenger important in many biological processes. is derived from adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway. adenylyl cyclase An enzyme that converts ATP to cyclic AMP in response to a chemical signal.

protein kinase A a serine/threonine kinase which is activated by cAMP (immediate effect) IP3 inositol triphosphate; binds to ligand-gated channels in the endoplasmic reticulum, opening them and releasing calcium into the cytosol DAG Diacylglycerol; membrane-bound second messenger that can be produced by cleavage of phophoinositides in response to stimulation of certain cell-surface receptors scaffolding proteins A type of large relay protein to which several other relay proteins are simultaneously attached to increase the efficiency of signal transduction. Apoptosis programmed cell death involving a cascade of specific cellular events leading to death and destruction of the cell caspase A “killer enzyme” that plays a role in apoptosis, or programmed cell death heredity The biological process whereby genetic factors are transmitted from one generation to the next

variation an organism that has characteristics resulting from chromosomal alteration genetics The scientific study of heredity and hereditary variation. Genes the units of inheritance that transmit information from parents to offspring gametes an organism’s reproductive cells, such as sperm or egg cells locus the specific site of a particular gene on its chromosome asexual reproduction reproduction that does not involve the union of gametes and in which a single parent produces offspring that are genetically identical to the parent

clone An organism that is genetically identical to the organism from which it was produced sexual reproduction reproduction involving the union or fusion of a male and a female gamete life cycle The generation-to-generation sequence of stages in the reproductive history of an organism. karyotype

A display of the chromosome pairs of a cell arranged by size and shape. homologous chromosomes chromosomes that have the same sequence of genes and the same structure. sex chromosomes X and Y chromosomes autosomes any chromosome that is not a sex chromosome diploid cell A cell containing two sets of chromosomes (2n), one set inherited from each parent. haploid cell A cell containing only one set of chromosomes (n). fertilization The union of haploid gametes to produce a diploid zygote. zygote

diploid cell formed when the nucleus of a haploid sperm cell fuses with the nucleus of a haploid egg cell

meiosis Cell division that produces reproductive cells in sexually reproducing organisms

alternation of generation An organism that has this pattern alternates between a haploid and a diploid generation sporophyte The multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation. Gametophyte The multicellular haploid form in organisms undergoing alternation of generations that mitotically produces haploid gametes that unite and grow into the sporophyte generation. meiosis I The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell. meiosis II The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell. Allele an alternate form that a gene may have for a single trait; can be dominant or recessive

synapsis The pairing of replicated homologous chromosomes during prophase I of meiosis. crossing over

exchange of genetic material between homologous chromosomes during prophase I of meiosis

chiasmata point of attachment between homologous chromosomes at which crossing over takes place

independent assortment of chromosomes In metaphase 1, when the homologous chromosomes are lined up on the metaphase plate, they can pair up in any of the homologous pairs facing either pole recombinant chromosomes A chromosome created when crossing over combines the DNA from two parents into a single chromosome. random fertilization source of genetic variation caused by the unlimited number of possible sperm & egg combinations