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Mitosis and Meiosis

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Chromosome
major carriers of genetic information in eukaryotes; consist of two chromatids bound by a centromere
Chromatin
the substance that makes up chromosomes: DNA wound around histone proteins and other associated proteins
Genome
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
Gene
a substance that provides information needed to carry out one or more specific cell functions
Histone
the enzyme that facilitates chromosome packing
Nucleosome
positively charged histones with negatively charged DNA (phosphate groups): structure
Scaffolding Proteins
nonhistone proteins that help maintain chromosome structure
Condensin
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
Interphase
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
Mitosis
nuclear division that yields nuclei containing chromosomes identical to that of the parent cell
Prophase
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
Centromere
the constricted region of chromosomes that joins the sister chromatids to form a chromosome
Cohesin
ring shaped protein complex that physically links sister chromatids
Kinetochore
a multiprotein complex found on the centromere; microtubules bound to centriole can attach to these to begin meta/anaphase
Microtubules
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
Centrioles
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
Asters
cluster of microtubules that migrate to opposite sides of nucleus; establish two poles of mitotic spindle
Metaphase
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
Karyotype
the chromosome makeup
Anaphase
chromosomes separate leaving the sister chromatids migrating towards opposite poles of the cell
Telophase
arrival of chromosomes at poles; at final stage cell returns to interphase conditions
Cytokinesis
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
Phosphorylating
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
p27
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
Cyclin
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
Clone
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
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
Diploid
condition of having two sets of chromosomes (2 pairs) per nucleus
Haploid
condition of having one set of chromosomes (1 pair) per nucleus
Polyploid
the condition of having more than two sets of chromosomes (multiple pairs) per nucleus
Meiosis
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
Synapsis
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)
Tetrad
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
Interkinesis
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
Gametogenesis
formation of gametes
Spermatogenesis
formation of four haploid sperm cells for each cell that enter meiosis
Oogenesis
formation of a single egg cell that enter meiosis