Cell Division And Connection By D Gnanasingh Arputhadas
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Transcript of Cell Division And Connection By D Gnanasingh Arputhadas
BT6303 CELL BIOLOGY
UNIT – II
CELL DIVISION AND CONNECTION
3RD SEMESTERDEPARTMENT OF BIOTECHNOLOGYBY GNANASINGH ARPUTHADAS.D
Contents Cell ------------------------------------------------------- 3 DNA vs RNA ------------------------------------------ 4 Chromosomes ----------------------------------------- 5 Cell Cycle ----------------------------------------------- 6 Mitosis --------------------------------------------------- 9 Meiosis -------------------------------------------------- 18 Mitosis vs Meiosis ----------------------------------- 20 Crossing Over ----------------------------------------- 21 Cell Junction ------------------------------------------- 22 Gap Junction ------------------------------------------ 23 Tight Junction ----------------------------------------- 24 Desmosomes ------------------------------------------- 25 Hemidesmosomes ------------------------------------ 26 References ----------------------------------------------- 27
CELL Cell is the basic structural, functional and
biological unit of all known living organisms
Often called as building blocks of life.
DNA
Double stranded A=T, G= C Carries genetic
information in most of the organisms
Single stranded A=U, G=C Carries genetic
information in some viruses
Types: messenger RNA transfer RNA ribosomal RNA
RNA
CHROMOSOMES
• Condensed DNA.
• DNA that is preparing to undergo cellular division
• Can now be seen with a microscope.
CELL CYCLE
G0 Phase
Interphase (90% of cell cycle)
Gap 1 (G1) Synthetic phase (S) Gap 2 (G2)
Mitosis (10% of cell cycle)
G0 PHASE
Resting phase
Cell leaves the cell cycle and stops dividing
G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.
Stages of Mitosis - IPMATC Interphase
• G-1: Maturation.
• S-Phase: DNA replicates - makes a duplicate copy of itself.
• G-2: Organelles replicate and final preparations for division.
MITOSIS
Division of the nucleus
Also called karyokinesis
Only occurs in eukaryotes
Has four stages
Doesn’t occur in some cells such as brain cells
Four Mitotic Stages
10
ProphaseMetaphaseAnaphaseTelophase
Stages of Mitosis - IPMATCProphase
• The chromatin condense to form visible chromosomes
• The nuclear envelope begins to dissolve
• The centrioles divide and begin to migrate to opposite sides of the cell
Stages of Mitosis - IPMATCMetaphase
• Centrioles have moved to opposite sides of the cell
• The spindle has formed
• Chromosomes are lined up in the middle of the cell across the equator
Stages of Mitosis - IPMATCAnaphase
• The centromeres split and the spindles pull the sister chromatids apart toward opposite sides of the cell
Stages of Mitosis - IPMATCTelophase
• The chromosomes move to opposite sides of the cell.
• The nuclear envelope begins to reform around each set of chromosomes at opposite sides of the cell.
Stages of Mitosis - IPMATCCytokinesis
• Division of the cytoplasm
• Begins to occur during telophase
• Different in plants and animal cells
Animal Mitosis
Plant Mitosis
MEIOSIS
Only occurs in sexually reproducing organisms
The goal of Meiosis is to produce gametes 2 cell divisions result in 4 daughter cells The chromosome number is halved Meiosis increases variability as no 2
gametes are the same Involves two successive divisions
Meiosis I Meiosis 2
MEIOSIS I vs MEIOSIS II
Mitosis vs Meiosis
Crossing over Crossing over consists of a mutual exchange of
equal quantity (segments) of chromosomal material between two non-sister chromatids.
CELL JUNCTION
GAP JUNCTION(COMMUNICATING JUNCTIONS)
Adjacent plasma membrane are closely opposed. intercellular space narrows upto
2-3 nm.
Gap junctions are made up of large protein units called CONNEXONS
Tight Junctions (Zonula Occludens)
"Zonula“ means band "occludens" = that
close off the space between the cells.
are the most apical of the junctions
Seal cells of an epithelial sheet to create a permeability barrier (MCQ)
Desmosomes“macula adherens”
This junctional type resembles a single "spot-weld" and does not form a belt around the cell
Cadherins: transmembrane proteins.
Bind intermediate filaments rather than actin filaments
Hemidesmosomes“Half-Desmosomes”
Adhere epithelial cells to the basal membrane
Integrins are the transmembrane proteins.
Anchor proteins link integrins to intermediate filaments
References
1. Alberts, Bruce, “Molecular Biology Of Cell”, 4th Edition, Garland Science, 2008.
2. Lodish, Harvey etal., “Molecular Cell Biology”, 6th Edition, W.H.Freeman, 2008.
3. Dr. Liz Williams, “The Journal Of Cell Biology”, Volume 194, No. 3, August 8,2011.
4. Kara Rogers, “The Cell”, 1st Edition, Britannica, 2011.
THANKYOU
Submitted toDr.P.Dhasarathan Ph.D,
Senior Assistant Professor,Department Of BioTechnology,
PITAM.