NCR-Cell Division and Cell Cycle

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Cell Division and Cell Cycle:

Cell Division and Cell Cycle Batch: Regular Duration: 120 mins For Queries, Contact support.biotecnika.org

References:

References Cell and Molecular Biology- Gerald Karp Molecular Cell Biology- Lodish For Queries, Contact support.biotecnika.org

Slide3:

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Control of the Cell Cycle- Work of Rao and Johnson G1-phase and an M-phase cell were fused- the chromatin of the G1-phase nucleus underwent premature chromosomal compaction to form a set of elongated compacted chromosomes G2-phase and M-phase cell were fused, the G2 chromosomes also underwent premature chromosome compaction the compacted G2 chromosomes were visibly doubled , Mitotic cell was fused with an S-phase cell Formation of “pulverized” chromosomal fragments observed For Queries, Contact support.biotecnika.org

Proteins involved in Cell Cycle Regulation:

Proteins involved in Cell Cycle Regulation Maturation promoting factor ( MPF ) Kinase activity- transfers phosphate groups from ATP to specific serine and threonine residues of specific protein substrates Cyclin - regulatory subunit For Queries, Contact support.biotecnika.org

Slide6:

Fig. Sequence of events for activation of cdk Regulation of cdk activity Cdk Inhibitors- e.g. Sic1 acts as a Cdk inhibitor during G1phase in yeast p21 and p27- inhibit cdk during cell differentiation Proteolysis of cyclin - by ubiquitin- proteasome pathway Subcellular Localization – in the nucleus For Queries, Contact support.biotecnika.org

Combinations between various cyclins & cyclin dependent kinases at different stages in the mammalian cell cycle:

Combinations between various cyclins & cyclin dependent kinases at different stages in the mammalian cell cycle For Queries, Contact support.biotecnika.org

Concept of Checkpoints:

Concept of Checkpoints surveillance mechanisms that halt the progress of the cell cycle if any of the chromosomal DNA is damaged , or certain critical processes, such as DNA replication during S phase or chromosome alignment during M phase, have not been properly completed Checkpoints are activated throughout the cell cycle by a system of sensors that recognize DNA damage or cellular abnormalities . If the DNA is damaged beyond repair , the checkpoint mechanism transmits a signal that leads either to the death of the cell or its conversion to a state of permanent cell cycle arrest (known as senescence ). For Queries, Contact support.biotecnika.org

An old Man’s Riddle:

An old Man’s Riddle For Queries, Contact support.biotecnika.org

Slide11:

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M Phase: Mitosis & Cytokinesis:

M Phase: Mitosis & Cytokinesis prophase, pro-metaphase, metaphase, anaphase, and telophase For Queries, Contact support.biotecnika.org

Prophase:

Prophase In vertebrates, cohesin is released from the chromosomes in two distinct stages. Most of the cohesin dissociates from the arms of the chromosomes as they become compacted during prophase . Dissociation is induced by phosphorylation of cohesin subunits by two important mitotic enzymes called Polo-like kinase and Aurora B kinase . For Queries, Contact support.biotecnika.org

Centrosome cycle:

Centrosome cycle

Slide18:

Prometaphase Chromosomal microtubules attach to kinetochores of chromosomes. Chromosomes are moved to spindle equator ( congression ) For Queries, Contact support.biotecnika.org

Attachment of the mitotic spindle at centromere:

Attachment of the mitotic spindle at centromere For Queries, Contact support.biotecnika.org

Metaphase:

Metaphase Chromosomes are aligned along metaphase plate, attached by chromosomal microtubules to both poles. For Queries, Contact support.biotecnika.org

The Spindle Assembly Checkpoint:

The Spindle Assembly Checkpoint Delays the onset of anaphase until the misplaced chromosome has assumed its proper position along the spindle equator Unattached kinetochores contain a complex of proteins (e.g. Mad2) Mediate the spindle assembly checkpoint. The presence of these proteins at an unattached kinetochore sends a “wait” signal to the cell cycle machinery that prevents the cell from continuing on into anaphase. Once the wayward chromosome becomes attached to spindle fibers from both spindle poles and becomes properly aligned at the metaphase plate, the signaling complex leaves the kinetochore, which turns off the “wait” signal and allows the cell to progress into anaphase . Delays the onset of anaphase until the misplaced chromosome has assumed its proper position along the spindle equator Unattached kinetochores contain a complex of proteins (e.g. Mad2) Mediate the spindle assembly checkpoint. The presence of these proteins at an unattached kinetochore sends a “wait” signal to the cell cycle machinery that prevents the cell from continuing on into anaphase. Once the wayward chromosome becomes attached to spindle fibers from both spindle poles and becomes properly aligned at the metaphase plate, the signaling complex leaves the kinetochore, which turns off the “wait” signal and allows the cell to progress into anaphase . Metaphase For Queries, Contact support.biotecnika.org

Metaphase-Anaphase transition :

Metaphase-Anaphase transition APC Cdc20 Securin Seperase For Queries, Contact support.biotecnika.org

Anaphase:

Anaphase Separation chromatids Mediated by anaphase promoting complex (APC Cdc20 ) Gets activated during metaphase Ubiquitinates securin (Anaphase inhibitor & helps in attachment between sister chromatids) at the end of metaphase Ubiquitination of securin produces separase Seperase cleaves cohesin Sister chromatids become separated Chromosomes move to opposite spindle poles. Spindle poles move farther apart. For Queries, Contact support.biotecnika.org

Telophase:

Telophase Chromosomes cluster at opposite spindle poles. Chromosomes become dispersed. Nuclear envelope assembles around chromosome clusters. Golgi complex and ER reforms. Daughter cells formed by cytokinesis. For Queries, Contact support.biotecnika.org

Cytokinesis:

Cytokinesis In animal cell In plant cell

Meiosis:

Meiosis An Overview For Queries, Contact support.biotecnika.org

Stages of Meiosis:

Stages of Meiosis Meiosis-I Prophase-I Leptotene Zygotene Pachytene Diplotene Diakinesis Metaphase-I Anaphase-I Telophase-I Meiosis-II Prophase-II Metaphase-II Anaphase-II Telophase-II For Queries, Contact support.biotecnika.org

Slide28:

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Three Groups differing in the phase at which meiosis occurs:

Three Groups differing in the phase at which meiosis occurs Gametic or Terminal Meiosis: Includes all multicellular animals and many protists , the meiotic divisions are closely linked to the formation of the gametes. Zygotic or Initial Meiosis: Includes only protists and fungi, the meiotic divisions occur just after fertilization t o produce haploid spores. Sporic or Intermediate Meiosis: Includes plants and some algae, the meiotic divisions take place at a stage unrelated to either gamete formation or fertilization. For Queries, Contact support.biotecnika.org

Prophase I:

Prophase I For Queries, Contact support.biotecnika.org

Slide32:

Leptotene Chromosomes become visible in the light microscope For Queries, Contact support.biotecnika.org

Slide33:

Zygotene visible association of homologues with one another i.e. synapsis accompanied by the formation of the synaptonemal complex ladder-like structure with transverse protein filaments connecting the two lateral elements (composed of cohesin ) The chromatin of each homologue is organized into loops that extend from one of the lateral elements of the SC Not involved in genetic recombination

Pachytene:

Pachytene chromosomes is called a bivalent or a tetrad characterized by a fully formed synaptonemal complex For Queries, Contact support.biotecnika.org

Diplotene:

Diplotene dissolution of the SC the chromosomes attached to one another at chiasmata (singular chiasma ) formed by covalent junctions between a chromatid from one homologue and a nonsister chromatid from the other homologue In vertebrates , diplotene can be an extremely extended phase of oogenesis during which the bulk of oocyte growth occurs. Thus diplotene can be a period of intense metabolic activity. Transcription during diplotene in the oocyte provides the RNA utilized for protein synthesis during both oogenesis and early embryonic development following fertilization.

Diakinesis:

Diakinesis Meiotic spindle is assembled Chromosomes are prepared for separation Recompaction of chromosomes takes place Diakinesis ends with the disappearance of the nucleolus, the breakdown of the nuclear envelope, and the movement of the tetrads to the metaphase plate For Queries, Contact support.biotecnika.org

Some Extra Information:

Some Extra Information The nuclear envelope may or may not reform during telophase I The stage between the two meiotic divisions is called interkinesis and is generally short-lived The progression of meiosis in vertebrate oocytes stops at metaphase II Brought about by factors that inhibit APC Cdc20 activation Leads to prevention of cyclin B degradation Leads to more concentration of active Cdks which do not allow cell to progress to Anaphase-II Metaphase II arrest is released only when the oocyte (egg) is fertilized Fertilization leads to a rapid influx of Ca2+ ions, The activation of APC Cdc20 , and the destruction of cyclin B For Queries, Contact support.biotecnika.org

Find the Presentation, Video and Questions :

Find the Presentation, Video and Questions www.study.biotecnika.org or www.study1.biotecnika.org NET JRF Video zone  CRC June 2015 Videos Regular Batch videos Unit 2 Cell Division and Cell Cycle Academic Team’s Helpline Number Find the Presentation, Video and Questions For Queries, Contact support.biotecnika.org

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