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major carriers of genetic information in eukaryotes; consist of two chromatids bound by a centromere


the substance that makes up chromosomes: DNA wound around histone proteins and other associated proteins


the presence of 100's or 1000's of genes in an organism

Human Genome Project

research group that predicts/estimates 25,000 protein coding genes in humans


a substance that provides information needed to carry out one or more specific cell functions


the enzyme that facilitates chromosome packing


positively charged histones with negatively charged DNA (phosphate groups): structure

Scaffolding Proteins

nonhistone proteins that help maintain chromosome structure


a group of proteins required for chromosome compaction

Cell Cycle

Stages through which cells pass from one cell division to the next

M phase

mitosis and cytokinesis; ensuring DNA is replicated for daughter cells; splitting of cell membrane


period of time when no cell division occurs; G1, S, G2

G1 phase

no DNA synthesis occurs; cell performs normal function, after mitosis/cytokinesis and before S phase

S (synthesis) phase

DNA is replicated and histone proteins are synthesized (cell then makes duplicate chromosome copies

G2 phase

increased protein synthesis; cell performs final cell functions (i.e. nerve cells, somatic cells); after S phase, before Mitosis/cytokinesis


nuclear division that yields nuclei containing chromosomes identical to that of the parent cell


chromosome compaction; long chromatin fibers begin coiling process (makes them shorter and thicker); nucleus dissipates

Sister chromatids

chromatids that contain identical double stranded DNA sequences coiled around histones


the constricted region of chromosomes that joins the sister chromatids to form a chromosome


ring shaped protein complex that physically links sister chromatids


a multiprotein complex found on the centromere; microtubules bound to centriole can attach to these to begin meta/anaphase


bound to centriole that later binds to the kinetochore of chromosomes; does the chromosomal division

Mitotic spindle

structure that separates the duplicated chromosomes during anaphase

Microtubule-organizing center

a region from which the microtubules extend to form the mitotic spindle


the organelle found in animal cells that are found in the middle of each microtubule-organizing center

Pericentriolar material

region of fibrils that surround the centriole and prevent the microtubules from actually touching the centriole


cluster of microtubules that migrate to opposite sides of nucleus; establish two poles of mitotic spindle


period of mitosis in which chromosomes align themselves at the cell's midplane

Metaphase plate

site of chromosomal alignment during metaphase

Polar microtubules

non-kinetochore microtubules; these extend from each pole to equatorial region (generally overlap here)

Kinetochore microtubules

these extend from each pole to attach to kinetochores around centromeres of chromosomes


the chromosome makeup


chromosomes separate leaving the sister chromatids migrating towards opposite poles of the cell


arrival of chromosomes at poles; at final stage cell returns to interphase conditions


division of cytoplasm in order to yield two daughter cells; overlaps mitosis and begins during telophase

Cleavage furrow

constricted region of cytoplasm that forms and progressively deepens during cytokinesis of animal cells, thus separating daughter cells

Cell plate

structure that forms during cytokinesis in plants, separating two daughter cells produced by mitosis

Binary fission

asexual reproduction by bacterium in which one cell divides into two offspring cells

Cell-cycle checkpoints

signals in the genetic program that ensure that all the events of a particular stage has been completed before beginning the next stage

Protein kinases

enzymes that activate or inactivate other proteins by phosphorylating them


addition of phosphate groups; protein kinases job to do this in cell regulation

Cyclin dependent kinases (Cdk's)

protein kinases involved in controlling cell cycle; activity increases and decreases during cell cycle

cyclin-Cdk complex

the region in which Cdk is associated with a specific cyclin; phosphorylate enzymes and other proteins


a protein known to be major inhibitor of cell division; degraded when phosphorylated

Anaphase promoting complex (ACP)

enzyme complex that is activated by M-Cdk toward the end of metaphase


regulatory proteins whose levels fluctuate predictably during cell cycle

Growth factors

those of protein which are active at extremely low concentrations; stimulate mitosis in some animal cells

Asexual reproduction

when one parent cell splits, buds, or fragments in order to produce two or more individuals


the offspring from a mitotic division that yields traits entirely similar to that of the parent cell

Sexual reproduction

union of two gametes to form a single zygote


the offspring of sexual reproduction

Homologous chromosomes

partner chromosomes in somatic cells (plant or animal), each similar in size, shape, and position of centromeres


condition of having two sets of chromosomes (2 pairs) per nucleus


condition of having one set of chromosomes (1 pair) per nucleus


the condition of having more than two sets of chromosomes (multiple pairs) per nucleus


type of cell division that reduces chromosome number; chromosome number reduced by one half

Meiosis 1

period of time within meiosis which consists of prophase, metaphase, anaphase, telophase; members of each homologous chromosome pairs join then separate and move into different nuclei

Meiosis 2

period of time within meiosis which consists of prophase, metaphase, anaphase, telophase; sister chromatids that make up each duplicated chromosome separate from each other, then distributed to two new different nuclei

Prophase 1

homologous chromosomes come to lie lengthwise side by side while chromatids are still elongated and thin


the process of physical association of homologous chromosomes during prophase 1 of meiosis

Maternal homologue

one of the members of each homologous pair of chromosomes (inherited from mother cell in production of zygote)

Paternal homologue

one of the members of each homologous pairs of chromosomes (inherited from father cell in production of zygote)


chromosome complex formed by synapsis of a pair of homologous chromosomes during meiotic prophase 1

Synaptonemal complex

a characteristic structure that forms along the entire length of synapsed homologues

Crossing over

a process in which enzymes break and rejoin DNA molecules, allowing paired homologous chromosomes to exchange genetic material

Genetic recombination

result of crossing over; greatly enhances genetic variation - new combination of traits

Chiasma (Chiasmata)

x shaped region in tetrads that marks the location where homologous (nonsister) chromatids previously crossed over

Metaphase 1

occurs when tetrads align on the midplain of the sex cell

Anaphase 1

the paired homologous chromosomes separate and move towards opposite poles; each pole receives random combination of maternal and paternal chromosomes

Telophase 1

chromatids generally decondense, nuclear envelope may reorganize, and cytokinesis may take place


period of time between meiosis I and meiosis II during which no DNA replication takes place

Prophase 2

similar to mitotic prophase; no pairing of homologous chromosomes, no crossing over

Metaphase 2

chromosomes line up on midplane of cells; opposed to TETRADS lining up

Anaphase 2

chromatids that are attached to spindle fibers at their kinetochores separate and move to opposite poles; like mitotic anaphase

Telophase 2

when one representative for each homologous pair at each pole; unduplicated single chromosome

Germ line cells

give rise to the next generation; gametes are developed when they undergo meiosis


formation of gametes


formation of four haploid sperm cells for each cell that enter meiosis


formation of a single egg cell that enter meiosis

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