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chapter 12
the cell cycle
| Term | Definition |
|---|---|
| Cell theory | in order for organisms to reproduce, grow, renew, and repair tissues there must be some way of reproducing new cells |
| The three ways cells can reproduce | mitosis, meiosis, binary fission |
| mitosis | Eukaryotic nuclear division; 2 daughter cells produced with the same number of chromosomes as parent cell |
| Meiosis | Eukaryotic nuclear division; 4 daughter cells produced with half the chromosome number as parent cell |
| Binary fission | prokaryotes. in bacteria |
| Composition of Eukaryotic chromosomes | 1 linear DNA molecule and proteins. 1:1 ratio by weight |
| Genome | all of the genetic material in a cell (humans=46 chromosomes) |
| Chromatin | unwound DNA and proteins; found in nucleus when cell is not dividing |
| chromosome | DNA and proteins; condensed chromatin= metaphase chromosome |
| 1st step of chromosome division | before a cell divides it duplicates its chromosomes. the 2 copies initially remain attached @ their centromes and are called sister chromatids. Each chromatid is a single DNA molecule identical to the DNA of the original chromosome before replication. |
| During the beginning of cell divisions | sister chromatids separate and each becomes and identical daughter chromosome |
| DNA packing | After DNA replication, but before nuclear division, DNA must be packed, sorted out, and moved into 2 daughter nuclei |
| To make chromosomes easier for division | they are folded and coiled therefore making them shorter |
| 1st step of DNA packaging | small positively charged histone proteins bind to negatively charged DNA |
| 2nd step of DNA packaging | DNA wraps twice around 8 histones forming a nucleosome; many nucleosomes form along 1 chromosome |
| 3rd step of DNA packaging | nucleosomes coil and fold forming a thicker fiber |
| 4th step of DNA packaging | the fiber forms looped domains around a protein scaffold |
| 5th step of DNA packaging | the looped domains coil and fold to form a typical metaphase chromosome |
| centromere | most chromosomes consist of 2 arms that extend out from a narrow specialized region of DNA. sister chromatids are bound her by a cohesin protein complex. |
| kinetochore | a small region of protein layers on the centromere with attachment sites for microtubules. cohesion breaks down after spindle fibers attach, except at the centromere |
| karyotype | chromosome of each species have characteristic shapes, sizes and staining patterns |
| Homologous chromosomes | pairs of chromosomes with the same genes. pairs are the same length, stain the same way but are not identical. one pair is some the female the other is from the male |
| diploid | cells with pairs of homologous. in humans 2n=46 in non-reproductive cells (23 pairs) |
| haploid | cell with only 1 copy of each chromosome |
| Cell cycle | cycle of events in the life of a eukaryotic cells from one division to the next |
| interphase | cell acquires nutrients from its environment, grows, makes proteins. and replicates its chromosomes. most of the life of the cell is spent in interphase. varies in length depending on the organism and cell type. |
| 3 sub phases of interphase | g phase, s phase, g2 phase |
| G1 phase | Fist gap in DNA structure. Follows cell division and preceded chromosome duplication. Production of proteins and organelles. occurs daily. 46 chromosomes |
| S phase | Synthesis. DNA replication(chromosome)sister chromatids are attached by cohesion. takes about half of the cell cycle. 2x46 chromosomes |
| G2 phase | Second gap. synthesis of non-DNA molecules needed for cell division (including centrosomes in animals). 92 chromosomes |
| Overview of Mitotic phase | one copy of each chromosome and about 1/2 of the cytoplasm, inc various organelles is dived into 2 daughter cells. produces 2 essentially genetic identical cells. |
| Subphases of mitotic division | Mitosis and cytokinesis. usually both occur but in some cells only mitosis |
| Mitosis | process of nuclear division that preserves the parental number of chromosomes |
| Cytokinesis | division of the cytoplasm |
| Steps of Mitotic phase | prophase, prometaphase, metaphase, anaphase, telophase |
| Steps of prophase | chromosomes begin to condense, nucleoli disintegrate, mitotic spindle forms. centrioles move to poles. often longest phase |
| Spindle fibers | specialized microtubules that guide the movement of chromosomes during mitosis. radiate from centrioles. |
| Centrosome | organize microtubules into spindle fibers |
| Steps of prometaphase | nuclear envelope disintegrates and chromosomes are released into cytosol. chromosomes finish condensing then are captured by spindle fibers.sister chromatid are attached to spindle fibers from opposite poles. chromosomes move to equator. |
| polar microtubules | hold the shape of the cell and support spindle fibers. |
| Kinetochore(protein) | located in each sister chromatid. found in its centromere. where spindle fibers attach. |
| Steps of metaphase | shortest stage. chromosomes line up along the middle of the cell w/1 kinetochore facing each pole. |
| Metaphase plate | the middle plane. |
| Anaphase steps | sister chromatids pull themselves apart. protein motors(Kinetochores) pull chromosomes to poles.Aster microtubules anchor centrosomes.spindle fibers disassemble into tubulin. other spindle fibers push the poles apart(oval shape) |
| Telophase | chromosomes reach poles. spindle fibers depolymerize, nuclear envelopes form around both full groups of chromosomes. chromosomes decondense. Nucleoli reappear. End of mitosis |
| cleavage (animal cells) part of cytokinesis | during telophase, microfilaments attach to the plasma membrane and form a ring around the cell. Ring contracts forming a cleavage furrow and divides the cytoplasm into 2 new daughter cells. |
| Cell plate formation (plant cells) Part of cytokinesis |
Created by:
ejohnson17
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