cell division. cell division consists of two phases: ● nuclear division ● cytokinesis = division...
TRANSCRIPT
![Page 1: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/1.jpg)
Cell Division
![Page 2: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/2.jpg)
Cell division consists of two phases:● nuclear division● cytokinesis = division of the cytoplasm
![Page 3: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/3.jpg)
There are two kinds of nuclear division:
●MITOSIS = creates two identical daughter cells●MEIOSIS = a reduction division that produces daughter cells containing half the genetic info. of the parent cell
![Page 4: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/4.jpg)
![Page 5: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/5.jpg)
![Page 6: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/6.jpg)
● During periods of non-cell division the genetic material exists in an uncoiled form called Chromatin
● Before cell division can take place the chromatin must begin to condense into tightly coiled bodies called Chromosomes
● Each chromosome is made of two identical halves called Sister Chromatids that are joined by a Centromere
![Page 7: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/7.jpg)
![Page 8: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/8.jpg)
![Page 9: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/9.jpg)
● Diploid Cells (2n): two copies of every chromosome; form a Homologous Pair
● Homologous Pair: one homologue is from the mother, one from the father
![Page 10: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/10.jpg)
● HUMANS = 46 chromosomes, 23 homologous pairs, 92 chromatids
![Page 11: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/11.jpg)
●When a cell is not dividing = chromatin is enclosed in the nuclear envelope●Microtubule Organizing Centers (MTOC) = Centrosomes contain a pair of centrioles used in cell division; located in cytoplasm●The non-dividing period of the cell cycle = INTERPHASE
![Page 12: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/12.jpg)
![Page 13: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/13.jpg)
![Page 14: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/14.jpg)
MITOSIS: there are four phases in mitosis = prophase, metaphase, anaphase, and telophase
PROPHASE:● Nucleoli disappear● Chromatin condenses into chromosomes● Nuclear envelope breaks down● Mitotic Spindleis assembled as Centrosomes
(MTOC) move toward the poles of the cell● Microtubules from the centrosomes connect to a
region of the centromere called the Kinetochore
![Page 15: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/15.jpg)
![Page 16: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/16.jpg)
Metaphase
●Chromosomes line up along the Metaphase Plate●Plate exists between the poles of the cell●Identical chromatids are attached to kinetochore fibers radiating from opposite ends of the cell
![Page 17: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/17.jpg)
![Page 18: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/18.jpg)
Anaphase
●Paired centromeres of each chromosome move apart●Move toward opposite ends of cell●Cell elongates●Result = 2 poles have identical collections of chromosomes
![Page 19: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/19.jpg)
![Page 20: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/20.jpg)
Telophase
●Concludes nuclear division●Nuclear envelope develops around each pole, forming 2 nuclei●Chromosomes uncoil into chromatin●Cytokinesis occurs – divides the cytoplasm into 2 cells
![Page 21: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/21.jpg)
![Page 22: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/22.jpg)
![Page 23: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/23.jpg)
●Once Mitosis is completed, Interphase begins.●Interphase is characterized as a period of growth.
Growth is divided into 3 periods: G1, S, G2 (G = Gap)
●G1 = growth and synthesis of non-DNA compounds like lipids, proteins, and carbs. Begins as soon as mitosis ends.
●S = DNA is synthesized as chromosomes are duplicated
●G2 = second growth phase, metabolic activities, preparation for mitosis
![Page 24: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/24.jpg)
![Page 25: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/25.jpg)
Fast Facts:
●90% of the cell cycle is spent in Interphase●A cell that does not enter the S phase will not divide●Mitosis is unique to Eukaryotes●Mitosis is reliable, only one error per 100,000 cell divisions
![Page 26: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/26.jpg)
MEIOSIS
●Cell division of the sex cells (gametes), sperm cell and egg cell●Consists of two groups of divisions (Meiosis I & Meiosis II)
![Page 27: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/27.jpg)
Interphase I :● Chromosomes replicate as in mitosis● Duplicated chromosomes consist of two
identical sister chromatids
![Page 28: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/28.jpg)
MEIOSIS I Prophase I:
● Nucleolus disappears● Chromatin condenses into chromosomes● Nuclear envelope breaks down● Spindle apparatus develops● Homologous chromosomes pair, a process
called synapsis● Pairs of homologues = Tetrads
![Page 29: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/29.jpg)
![Page 30: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/30.jpg)
![Page 31: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/31.jpg)
Synapsis
●During synapsis, corresponding regions along non-sister chromatids form close associations called Chiasmata = sites where genetic material is exchanged●Crossing Over= the exchange of genetic material between non-sister chromatids
![Page 32: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/32.jpg)
Metaphase I:● Homologous pairs are lined up at the
metaphase plate● Microtubules extend from one pole and attach
to centromere (kinetochore) of one member from each homologous pair
![Page 33: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/33.jpg)
Anaphase I:● Homologues within tetrads uncouple● Move towards opposite poles
![Page 34: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/34.jpg)
Telophase I:● Chromosomes have reached poles● Nuclear envelope redevelops● Each pole has half the number of chromosomes● Each chromosome contains 2 chromatids● Cytokinesis follows● Interphase II may follow (no duplication)
![Page 35: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/35.jpg)
Prophase II:● Nuclear envelope disappears● Spindle fibers form● NO CROSSING OVER!
![Page 36: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/36.jpg)
Metaphase II:● Chromosomes align singly at the Metaphase
plate
![Page 37: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/37.jpg)
Anaphase II:● Each chromosome is pulled apart into 2
chromatids● Chromatids migrate to poles
![Page 38: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/38.jpg)
Telophase II:● Nuclear envelope reappears● Cytokinesis occurs● END RESULT = 4 Haploid daughter cells
![Page 39: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/39.jpg)
Genetic Variation
●Occurs as a result of meiosis = Sexual Reproduction●Reassortment = Genetic Recombination; 3 events are responsible:●Crossing over: Occurs during Prophase I; non-sister chromatids of homologous chromosomes exchange pieces of genetic material●Independent Assortment of Homologues: random separation during Metaphase I●Random Joining of Gametes: which sperm cell fertilizes the egg is random
![Page 40: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/40.jpg)
![Page 41: Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm](https://reader033.vdocuments.site/reader033/viewer/2022061614/56649e545503460f94b4b8b7/html5/thumbnails/41.jpg)
Why Do Cells Divide?
●Maintain a low surface area to volume ratio●Many microscopic cells are more efficient than a few large ones●Maintain a low genome to volume ratio (genome controls the cell)●Density Dependent Inhibition= cell division stops when cell density reaches a certain maximum