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
Condensed DNA. DNA that is preparing to undergo cellular division Can now be seen with a microscope.
G0 Phase Interphase (90% of cell cycle) Gap 1 (G1) Synthetic phase (S) Gap 2 (G2) Mitosis (10% of cell cycle)
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.
G-1: Maturation. S-Phase: DNA replicates - makes a duplicate copy of itself. G-2: Organelles replicate and final preparations for division.
Division of the nucleus Also called karyokinesis Only occurs in eukaryotes Has four stages Doesnt occur in some cells such as brain cells
10 Prophase Metaphase Anaphase Telophase
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
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
The centromeres split and the spindles pull the sister chromatids apart toward opposite sides of the cell
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.
Division of the cytoplasm Begins to occur during telophase Different in plants and animal cells
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
Crossing over consists of a mutual exchange of equal quantity (segments) of chromosomal material between two non-sister chromatids.
Adjacent plasma membrane are closely opposed. intercellular space narrows upto 2-3 nm. Gap junctions are made up of large protein units called CONNEXONS
"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)
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
Adhere epithelial cells to the basal membrane Integrins are the transmembrane proteins. Anchor proteins link integrins to intermediate filaments
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.
Submitted to Dr.P.Dhasarathan Ph.D, Senior Assistant Professor, Department Of BioTechnology, PITAM.
