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The Mitotic Cell Cycle, chromosomes, centromere, telomere, chromosomes…

- - - - these threads have the ability to carry out self replicating
        
        so they have a specific organisation and individuality
  - - - dna
      - rna
    - - acidic proteins - fm acidic amino acids
      - neutral proteins - fm neutral amino acids
      - largely basic proteins (histones) - because of large amounts of lysine and arginine - basic amino acids forming it
    - - dna polymerase or rna polymerase
    - - phosphoric acid group, etc
  - - - later called chromosomes because chroma - colour and soma - body - since they absorb the stain colour easily to see in a microscope
        
        scientists finally proved that they carry genetic information
  - - - in humans - 23 pairs - continues in all species
    - - two sets - diploid
        
        number of chromosomes - 23
    - - like gametes have only half the number
        
        diploid number is '2n'
        
        haploid number is 'n'
  - - - no chromosomes seen in inter phase
        
        by looking at shape of chromosomes you can tell whether cell is dividing or not
        
        when not dividing - extremely thin threads of chromatic material
        
        when dividing - undergo coiling - become short and thick - so can take up colour - then it is easily visible
    - - called constriction
        
        has 3 diff types of constrictions - the main one - primary - runs along length of chromosome - appears as a narrow, almost non-stained region
        
        in primary constriction there is a centromere in the center
        
        centromere
        
        has a protein-rich granules which make up a region called kinetochore where microtubes of chromosomal spindle fibres attach to
        
        chromosomes have a tendency to move to equator/ the poles
        
        because of attachment of microtubules to the spindle fibres
        
        in cell - spindle apparatus with centre and poles
        
        important function
        
        divides the chromosomes into 2 parts on 2 sides - chromatids
        
        divided into the arms - chromatin threads
        
        nucleation polymerization of tubulin protein to make microtubules
        
        centromere position - method used to identify evolution changes across species
        
        region where the attachment of spindle fibres take place
        
        primary constriction is called the centromere
    - - in the interphase - extremely thin and thread like - hard to see
      - shape and size changes through the stages
    - - named based on different things -
        
        depending on ability of centromere to divide into 2 parts/ its position
        
        heterobrachial
        
        position of centromere isn't in centre - unequal lengths of chromatin
        
        isobrachial
        
        centromere is in the centre
        
        location
        
        nuclear
        
        inside the nucleus of eukaryot
        
        extranuclear
        
        seen in autonomous organelles which have their own chromosomes - mitochondria, chloroplasts, etc
        
        no of centromeres present
        
        monocentric
        
        only one centromere
        
        bicentromeric
        
        2 centromeres
        
        polycentric
        
        more than 2 centromeres on the chromosome
        
        a-centric
        
        no centromeres - they represent freshly formed fragments, they just lie in the cytoplasm, they don't participate in cell division
        
        holocentric (aka polycentric)
        
        several centromeres
        
        along entire length of chromosome
        
        spindle attaches to more than one part of the chromosome
        
        shape of chromosomes
        
        depends on where the centromere is present
        
        centromere in extreme end of it/ terminal end
        
        only one long chromatin
        
        telocentric (tail) chromosome/ eye-shaped chromosomes
        
        2 more items...
        
        centromere is not terminal - sub terminal having two chromatins - one chromatin is very long, other is very short
        
        acrocentric/ j-shaped chromosomes
        
        p arm - short, q arm - longer
        
        one is longer, other is verryy small
        
        most chromosomes - centromere is in centre - so 2 equal sized arms/chromatins
        
        metacentric/ v-shaped
        
        all are isobrachial chromosomes
        
        not right in centre - slightly away
        
        heterobrachial
        
        one is large, other is relatively small
        
        1 more item...
    - - narrow region, non stainable
      - called nucleolar organiser region coz they have genes - for synthesis of 80s and 20s ribosomes in the nucleolus
      - like primary - its position is constant, so used to study evolution relationships
    - - its position is also constant - can be used to study evolutionary relationship
    - - ends are rounded - sealed
        
        like sealed shoelaces
      - functions
        
        important - it ensures individuality of chromosomes is maintained
        
        prevents it fm entering into any permanent/ temporary relationships with homologus/ non-homologus chromosomes - during cell division
        
        most important function
        
        prevents loss of vital information/ keeps constant
        
        ensure that important genes won't get lost, since they are at the end, and during cell division they could get lost
        
        makes an enzyme called telomerase
        
        adds nitrogen bases to the ends of the dna molecule, which has no important genetic information, and does not carry any info - so called junk dna
        
        dna becomes larger
        
        now it fools dna p (enzyme) into removing the junk bases - its fine if these are lost
        
        1 more item...
        
        makes cell immortal
        
        eg: cancer cells, kill the body, but they wont die, because they produce telomerases, so the cancer cell's dna isn't removed
        
        provide stability to the chromosome
      - as person gets older - few genes are lost
        
        eg - less eyesight, more diseases, loses sense organs - lose control over some things
        
        lost as person gets older
    - - terminal ends of chromosomes beyond secondary constriction
      - round or knob shaped - like the smallll end in the acrocentric chromosomes
      - attached to main body by a delicate chromatin filament
      - chromosomes that have satellites - are called sat chromosomes
- - - - m phase, mitotic phase/ karyokinesis - division of nucleus
        
        cytokinesis
        
        animal cell
        
        formation of cell furrow
        
        during mitosis - in late telophase, after mature mother cell has duplicated genome and made things needed to divide (requirements like food etc.)
        
        then cleavage/ furrow forms
        
        in the equatorial region (equator) - cleavage furrow forms
        
        appears because of peripheral band of microfilaments in equatorial region
        
        the band contracts/ constricts
        
        1 more item...
        
        band of microfilaments - tubulin
        
        centripetal (fm outside to inside)
        
        formation of cleavage furrow proceeds fm the periphery to the centre of the cell
        
        in a plant cell
        
        no cell membrane
        
        can't form cleavage furrow, since membrane needs to bend, and cell wall is rigid
        
        appearance of cell plate
        
        indicated (represented) by middle lamella (it forms the middle lamella between adjacent/split/newly divided cells)
        
        like band of microfilaments, golgi bodies area used in equatorial region (where cell plate forms)
        
        specialised organelles associated with secretion
        
        secretes vesicles
        
        1 more item...
        
        not necessary that all vesicles fuse completely
        
        some places where the vesicles don't fuse
        
        zone of continuity
        
        1 more item...
        
        centrifugal - since cell plate forms from centre (equatorial region of cell) and moves to periphery of cell
        
        comparison between cytokinesis plant and animal
        
        similarities
        
        both have a mature mother cell that divides (has to duplicate its genome and all other organelles), after synthesising all requirements
        
        differences
        
        process
        
        A - formation of cleavage furrow
        
        P - golgi bodies secrete vesicles that fuse and form cell plate
        
        direction
        
        A - cleavage forms along the periphery and then moves through the centre - centripetal
        
        P - formation of cell plate is fm centre and then to the periphery/ divides it in the centre itself - centrifugal
        
        contractile ring
        
        only in animal cells
        
        1 more item...
        
        not in plants
        
        1 more item...
        
        formation of cell plate
        
        in plants
        
        not in animals
        
        cell wall
        
        only in plants
        
        not in animals
        
        mitotic phase
        
        m phase
        
        the actual dividing phase
        
        karyokinesis - splitting of nucleus
        
        after cytokinesis
        
        2 more items...
        
        diff parts
        
        1 more item...
        
        24 hours
        
        biological importance of mitosis
        
        results in 2 genetically identical daughter cells
        
        maintains number of chromosomes
        
        ensuring genetic stability
        
        new cells can retain functions
        
        growth of multicellular organisms
        
        cell replacement and tissue repair
        
        asexual reproduction, eg vegetative reproductive in plants/ cloning
        
        prophase
        
        sometimes prometaphase
        
        metaphase
        
        arranging
        
        chromosomes get arranged in the equatorial region
        
        1 more item...
        
        organisation phase
        
        centrosomes reach opposite poes
        
        spindle fibres are fully formed
        
        1 more item...
        
        anaphase
        
        centromere of each chromosome divides
        
        1 more item...
        
        shortest phase
        
        telophase
        
        4 more items...
        
        condensation of chromatin
        
        becomes shorter and thicker
        
        appear as chromosomes
        
        visible as 2 sister chromatids
        
        spindle fibres form
        
        centrosomes move to opposite poles
        
        nuclear envelope breaks down
        
        nucleolus breaks down in prometaphases
        
        spindle fibres just starting to move
        
        in prometa - they have moved to poles
        
        longest phase
      - interphase/ preparatory phase
        
        interval between 2 successive divisions of a eukaryotic cell - part of cell cycle when the chromosomes are seen in the form of thin chromatin threads
        
        not in the form of chromosomes - thin chromatin network
        
        can't see chromosomes in nucleus
        
        was called resting phase - no visible changes in the cell
        
        might not be visible changes, but cell is metabolically and biosynthetically active
        
        produces components (proteins, nucleotides, etc) needed to divide later - so called preparatory phase, not the resting phase
        
        3 phases
        
        g1 phase (1st growth)
        
        s (systhesis)
        
        g2 (second growth)
        
        increase in size of cell, and number of energy molecules (atp, energy-rich nucleotides) increase
        
        RNA
        
        1 more item...
        
        organelles
        
        1 more item...
        
        protein
        
        1 more item...
        
        DNA
        
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        2-5 hrs
        
        replication of dna
        
        denaturation - h bonds between bases broken - polynucleotide chains broken
        
        semi-conservative mechanism - only 1 strand conserved
        
        1 original strand
        
        only 2 chromatids before
        
        1 more item...
        
        dna is doubled
        
        AT bases - 2 hydrogen bonds
        
        GC bases - 3 hydrogen bonds
        
        6-8 hours
        
        no options for the s phase
        
        aka post mitotic phase/ pre-synthesis phase - immediately after mitosis
        
        the stage between two - after mitotic and before synthesis
        
        increase in size and volume of cell
        
        cell is synthesising many biological/chemical molecules
        
        intense bio activity
        
        when formation of several organelles
        
        dna content
        
        remains constant
        
        it hasn't replicated or divided yet
        
        3 options now
        
        cell continues participate and undergo division
        
        get arrested at any point and
        
        go into G0 phase (opt out of cell cycle)
        
        1 more item...
  - - - some 20 mins
- - - - forming chromatin fibre
        
        which finally forms chromosomes
  - - - segment of dna that codes for a protein
    - - position of a gene in a chromosome
    - - pair of chromosome
      - pairs of chromosomes found in diploid cells
      - 1 maternal 1 paternal
      - similar centromere position
        
        similar chromosome size and shape
        
        same genes different alleles
    - - 2 genes for same feature, but one dominant, 1 recessive
      - different forms of one gene
    - - during interphase, dna duplication happens in nucleus
      - 1 chromatid becomes 2 - two identical chromatids (sister chromatids)
      - appears in the synthesis phase in the interphase
      - thay have identical copies of genes
      - the centromere holds 2 chromatids together
      - later breaks into 2 for the 2 new daughter cells
- - - - only somatic cells - mitotic
        
        anything to do with growth and evelopment of cells - directly linked to mitosis
        
        germ cells is meiosis
      - in animals - continuous process
        
        each part grows
      - different for plants
        
        growth is concentrate in tip of root and shoot
        
        because of meristramatic tissues
    - - increases in size
        
        nucleo-cytoplasmic ratio
        
        if cell becomes too large, nucleus cannot controo activities
        
        to make sure nuclueus still has control
        
        once ratio die=srupted, cell undergoes division
      - ensure that cell size is always optimum
        
        transformation
        
        efficient use of energy transformation and availability of food, formation of new cytoplasm
    - - genetic stability
        
        maintainenace of chromosomal number
        
        meiosis also
    - - constantly subjected to wear and tear
        
        all damaged cells need to be repaired
        
        ensures that there is repair replacement and regeneration of damages or dead cells
        
        by mitotic division
    - - not in m,ulticellular - ususlly for growth and repair
      - in unicellular
        
        amoeba, yeast
        
        mitosis is a method of asexual reproduction
        
        like binary fission in bacteria
        
        budding in yeast
    - - any prokaryot or eukaryot
        
        involes all prophase anaphase in the exact order
        
        tells us that all organisms have evolved fm a commmon ancestor
        
        indicated evoluationary relationships
    - - 2 types of lymphocytes
        
        B and T
        
        they divide by mitosis
        
        role in decidint immune response
        
        form clones by mitosis
- - - - they can form clones (self replication or self-renewal)
        
        also get differentiated to form many idfferent functions
  - - - parents, ancenstor, mother of all cells
        
        can give rise to different cells
    - - form different types of cells fm different lines
        
        form differnet cells
    - - find a possible cure
      - eg leukemia, parkinsons
      - like blood cells or neural cells - for parkinsons
        
        haemotopoietic stem cells and neurogenic stem cells
  - - - as organs and systems become more complex, some cells which could divide, lose their ability to divide - don't know how to divide anymore
      - ability of undifferentiated normal unspecialised cells to become specialised
      - depending on potency, cells divided into 5 main types
      - 200 diff. cells
    - - totipotent
        
        can form all types of cells including stem cells, not only embryonic
        
        zygoform in last to last stage, gas to last stage, and then embryo forms fetus
        
        egg
        
        zygote
        
        morula (16)
        
        blastula
        
        gastrula
        
        1 more item...
        
        formed in initial stages of division
        
        formed fm the 16th cell stage (morula)
      - pleuripotent
        
        can form all cells of an organism (any body cells) except embryonic stem cells
        
        obtained fm blastula stage
        
        cells at periphery
        
        blastomeres (the outer circle) and inner cell mass (inside the circle) - forms the embryo
        
        inner cell mass - blastomeres
        
        ectoderm
        
        mesoderm
        
        endoderm
        
        harvested fm blastomeres, the inner cell mass and 3 inner germ layers
        
        descendant of totipotent
      - multipotent
        
        all which can give rise to a number of cells, but only to cells that belong to one particular family
        
        haemapoietic
        
        give rise to lymphocytes, rbcs, neutrofils, basofils - all belong to one category - the blood cells
      - oligopotent
        
        oligo meaning 'few'
        
        can give rise to few other types of cells
        
        eg
        
        lymphoid stem cells
        
        myeloid stem cells
        
        but fm different families
      - unipotent
        
        uni means 'one'
        
        can give rise to only one type of cell
        
        stem cell initially has 2 options
        
        diff or self renewal
        
        and are also capable of only cell renewal
        
        eg
        
        muscles
        
        1 more item...
        
        the only one that can do self-renewal
  - - - important for repair, regeneration and recovery of
        
        depending on physiological needs of cells
      - capable of adapting themselves to different needs
        
        to different physiological conditions
      - in endocrine glands
        
        needed for secretion of hormones
      - b lymphocytes, t lymphocytes
        
        for immune system
        
        stem cells are neede
      - for general maintenance of organism
        
        stem cells necessary
        
        eg
        
        blood cells in. body
        
        250 M wbcs destroyed, 20 M rbcs destroyed
        
        to counter, haemapoietic stem cells are used
  - - - embyronic stem cells
        
        totipotent
        
        can form any cell of the body
        
        fm blastula/ and morula gastrula, after all the 3 stages
        
        blastomeres and inner cell mass, and germ layers
        
        embryos are fertilized zygotes 4-5 days after fertilization
        
        source
        
        fm fertility clinics
        
        in vitro
        
        healthy ones are implanted
        
        not healthy ones are used to harvest stem cells
        
        also used in transplants
      - foetal stem cells
        
        the embryo. after 8 weeks of fertilization
        
        converted to fetus
        
        most primitive
        
        present in fetal organs
        
        source
        
        foetal proper stem cells
        
        kind which obtained directly fm foetus
        
        eg after abortion
        
        releases these kinds of stem cells
        
        not immortal but multipotent
        
        can degenerate after a time
        
        extra embryonic stem cells
        
        obtained fm extra embryonic membranes
        
        eg
        
        amnion
        
        chrion
        
        allentois
        
        umbilical
        
        placenta
        
        pleuripotent
      - adult stem cells
        
        description
        
        needed for generla maintenance of body
        
        in chidren and adults, but lessser in number in children
        
        aka somatic stem cells
        
        source
        
        fm bone marrow of large bones
        
        fm amniotic fluid
        
        nomenclature
        
        adult stem cells are named based on tissues
        
        treatment
        
        important
        
        when injurgy to spinal cord
        
        liver sclerosis
        
        degenerative diseases of spinal cord
  - - - multiple organ failures
      - scid - severe
    - - leukemia - blood
        
        haemapoietic stem cells used to treat
      - lymphoma
        
        lymphoid
    - - born with
        
        sickle cell anaemia
        
        congenital disorders
      - thalassmia
        
        decrease in haemoglob count
    - - subjected to chemo, reduction in amount of bone marrow
      - increase no./amount of bone marrow
    - - when body produces antibodies against own organs
        
        eg
        
        diabetes
        
        parkinsons
- - - - it always has a specific purpose and moves in a very controlled manner
      - in most parts of the body where cells differentiate, except liver and brain
        
        they indergo mitotic division
        
        to repair
        
        when dividing normally
        
        its always for a purpose
        
        when division becomes purposeless
        
        no longer under control of body
        
        cancerous cells form
      - for growth and repair of damaged and degenerated parts
    - - cancer
        
        a cancer cell survives at the expense of normal cells
        
        aka neoplastic (abnormal) cells
        
        all cancers are tumurous
        
        it is the spread of abnormal cells
    - - an undifferentiated mass of tissues which is formed by uncontrolled division of cells
      - not all tumours are cancerous
      - when a group of cells begins to spread
    - - every organ in a mammal is capable or undergoing oncogenic (cancerous) transformation
        
        every cell organ has potential cancer cells
        
        but most common are cancer of bone marrow, breast cancer, lungs, uterus, cervix, prostrate gland
        
        oncogenic
        
        when normal cell becomes cancerous
    - - process by which normal cells (proto-oncogen) gets converted into a cancerous (malignant/ oncogen) - carcinogenesis
      - agents which cause carginogenesis are called carcinogen
  - - - carcinoma
        
        90% of cancers
        
        cancer of epithelial cells
        
        most common
      - sarcoma
        
        cancer of muscles/ bones/ connective tissues
        
        2% - rarest incidents of cancer
      - melanoma
        
        cancer of melanocytes
        
        melanin forming cells
        
        mostly present in skin
        
        less common based on exposure
        
        to uv etc
        
        variable %
      - leukemia
        
        cancer of blood cells
        
        rbcs or wbcs
        
        8%
      - lymphomia
        
        cancer of cells of immune system - b and t lymphocytes
  - - - benign
        
        localised
        
        so can be treated
        
        small
        
        resemble any normal cell in structure and function
        
        one difference
        
        sheer bulk - their size
        
        ability to secrete certain types of hormones - in large amounts
        
        call them tumours not cancers (not malignant) since they are not differentiated cells
        
        still dangerous
        
        since some can get converted into malignant
      - malignant
        
        characterised by cells capable of rapid division
        
        properties differ based on where they originated from
        
        dangerous since they can invade the surrounding normal cells
        
        unique
        
        metastasis
        
        90% deaths of cancer
        
        establishing secondary area of growwth
      - differences
        
        nature
        
        benign cancer is composed of single layer (single mass) of rapidly dividing cells, but is covered by a capsule, so it cant grow onto other cells
        
        malignant - multiple layer is rapidly dividing neoplastic cells
        
        not encapsulated
        
        easily spread fm one region to another
        
        growth
        
        benign - divide slowly compared to malignant
        
        after some time it stops
        
        malignant is capable of rapid continuous growth/ division
        
        doesnt stop
        
        invasiveness
        
        benign is capsulated, so do not invade other cells
        
        malignant - no capsule so can infect/ grow onto other cells - metastasis
        
        migratory
        
        benign cant migrate since capsule
        
        non cancerous
        
        malignant - capable of spreading
        
        so called cancerous - divide and spread
        
        cancerous
        
        benign dont show metastasis
        
        malignant - its important property is metastasis
        
        latent period
        
        metastasis - ability to spread
        
        person exposed to factor
        
        period of time between exposure to initiator and progression of disease cancer
        
        benign no latent period
        
        since capsule
        
        for malignant there is a period
        
        causes of cancer
        
        any agent capable of causing cancer - carcinogen
        
        smoking
        
        irritation of mouth, trachea, voice
        
        not only because or nicotine
        
        but tar
        
        cancer of mouth, throat, and larynx
        
        chewing of tobacco
        
        irritation of buckal cavity - mouth
        
        irritation of epthlieal cells
        
        common in Kashmir
        
        traditional earthen pot called kangiri
        
        1 more item...
        
        broken tooth
        
        in crease of broken tooth tongue gets irritated can cause a cancer
        
        irritation is a carcinogen
        
        chemicals
        
        pesticides, heavy metals, excessive doses of sex hormones, steroids, asbestos mining, accumuate in lungs - mesotheryoma
        
        ionizing radiation
        
        x rays, gamma rays
        
        can break down the nitrigen bases in dna and induce mutation
        
        viruses
        
        burkitts lymphoma
        
        hpv
        
        hpv human
        
        pappiloma
        
        epstein bar
        
        herpes simplex type 2
        
        hereditary
        
        high incidents of certain cancers
        
        inheritance of gene that results in cancer
        
        can be dominant or recessive
        
        genetic presisposition
        
        forms of carcinogens
  - - - when a normal cell grows, it recieves a signal fm ourside - signalling
        
        if a normal doesn't recieve, it doesnt divide
        
        depends on a growth signal
        
        stimulus to divide
        
        mechanism of the body to prevent any extra, uncontrolled growth
      - cancer generated own growth signals
        
        so grow in a manner completely different to normal body
        
        then grow at a rate uncontrolled by the body
        
        becoming an organism of their own within the body
        
        unorganised manner
    - - failure to respond to stop signals
      - 2 adjacent cells
        
        cell membranes in contact
        
        respect each others space
        
        don't grow over each other
        
        stop when they touch each other
      - but cancerous cell grows over and above the cell it comes in contant with
        
        no contact inhibition
    - - every cell in the body can divide but only finite no of times then stops
      - cancer cell can undergo diviisons repeatedly (infinite) without losing dna
        
        telomeres works better then normal cells
    - - programmed cell death
      - initially very active, but normal cell after a poitn of time gets damaged
        
        mechanism to identify damaged and destroys cell - breaks it into fragments - destroys genome, cellular debris
        
        removed by phogocytosis
      - avoids apop, cell death, as long as it can, it only divides, never dies
        
        because of telomerases
      - in chemo, induces cancer cells to die
    - - when cancers multiply - more cells in a particular area
        
        demands become high
        
        oxygen and nourishment needed
        
        initially, environment lacks oxygen
        
        generated molecular signals
        
        blood vessels go towards the cancer
        
        so gets room service for cancer
        
        cancer grows very easily now with extremely abundant materials
        
        hypoxic environment
        
        1 more item...
        
        positive feedback
        
        more cancer, more o2 used
        
        this property make it neoplastic
    - - grow on others/surrounding cells
  - - - what kills the patient - growing over other cells
    - - intravasation
        
        into the blood
        
        all cells always have a platform on which they are arranged - basement membrane
        
        close to blood vessel
        
        cells are arranged in an interlocking position
        
        cells obtain nourishment fm the cells close to vessel
        
        which get nourishment fm the blood
        
        live in a group
        
        addition molecules - molecules on the surface of the cell
        
        compact and close
        
        addition molecules link these moleules together
        
        addition molecules are in normal cells
        
        if one cell moves away fm the others, it dies, since its not in contact with other cells with the blood vessel, as it loses the addition molecule so it can't attach again
        
        so it dies, since its nourishment is cut off
        
        but a cancerous cell, when it moves away fm the others cells, it maintains the addition molecule, unlike the other cells (who lose it)
        
        finds its way into a blood vessel through gaps in the blood vessel
        
        now its bathed in nutrients, so can grow extremely easily
        
        all cancerous cells get into the blood
        
        but even if its not in the blood it can still survive since it retains the addition molecules on its surface, so can attach anywhere
        
        in the blood - dissemination
        
        its in the blood now
        
        high pressure, normal cells can't survive, or even think of getting in
        
        but different kinds of cells are in the blood
        
        like wbcs, which come to regulate/ destroy the cancerous cells
        
        so cancerous cover themselves with the blood platelets - it acts as a shock absorber fm the pressure
        
        2 more items...
        
        co-opting
        
        extravasation
        
        then, 'cancer cell covered in platelets' creates the gaps in the platelets, to get all its nutrition to divide easily (because it needs oxygen and nutrients)
        
        so cells divide uncontrollably and form a large tissue (tumour?) (too bog for the capillaries)
        
        when diameter is too narrow, it gets stuck in the capillaries, so blood flow stops, and it removes more of the platelets, to get more nutrition and grow
        
        2 more items...
        
        out of the blood
        
        organ targeting
        
        trying to match its addition molecules
      - if breast can cer isn't detected early, person might die fm lung cancer instead, since the cancer spread through the bkolood, etc
        
        relapse of cancer - cancer went to another organ
  - - - proto-oncogenes
        
        any cell is capable of becoming cancerous
        
        these are called proto-oncogens
        
        not yet oncogens, but could bcome - proto
        
        if exposed to carcinogens,
        
        when exposed to carcinogens, it can induce mutations in the dna/genetic material
        
        can cause uncontrolled cell division
      - tumour promoter
        
        when protoonco exposed to cancinogen
        
        in quiescent/ dormant state
        
        becomes active n the presence of growth hormones/ genes
        
        when activfated, ability to grow abnormally growth or uncontrolled division
        
        sex hormones, steroids, etc
        
        initially a protoonco
      - tumour supressor
        
        remains active only in a non dividing cell
        
        exposure to carcinogen/ mutation
        
        starts stimulating production of tmumuour cells/ new types of cacners
        
        instead of supressing, it promotes
        
        supposed to fight the tumour, but instead it promotes the tumour
      - different stages
      - viral oncogens
        
        diff kinds of viruses
        
        epstein bar virus - ebv
        
        causes lymphoma cancer
        
        human pappiloma virus - hpv
        
        causes cervical cancer
        
        herpes simplex type 2 virus -
        
        when thess viruses cause cancer
        
        viruses are proteins
        
        inject host cells with viral oncogenes
        
        viral dna injected, viruses use an enzyme called intergrase
        
        intergrates the viral oncogenes onto the normal cells called protooncogenes
        
        then protooncogens get converted into oncogens - can indergo uncontrolled division - leads to carcinogenesis - formation of new cancerous cells
  - - - Stage 1: initiation stage
        
        exposed to an initiator - carcinogen
        
        dna undergoes mutation
        
        proto-oncogen becomes an oncogen
        
        divides uncontrollably
        
        develops the ability to divide uncontrollably
        
        unnoticed
      - Stage 2: promotion stage
        
        must be one more factor exposed to which can accelerate mutation/ tumour formation
        
        eg, person exposed to paints with volatile organic compounds - carcinogenic - initiator
        
        but he is a smoker, so tar in the cigarettes is a carcinogen, so initiator gets aggravated
        
        cells undergo repeated mutation and divide to form tumourous growths
        
        acquire the ability to form a tumour
        
        promoter
        
        it could also be a initiator
        
        and there could also be only one initiator, but it would take time
        
        1 more item...
      - Stage 3: tumour development
        
        person begins to start showing symptoms
        
        characterised by two things
        
        neoplasia
        
        new growth of cancerous cells
        
        aplasia
        
        cells divide so rapidly the they resemble embryonic cells - undifferentiated
        
        appearance of tumour formation
        
        undifferentiated mass of tissues
      - Stage 4: metastasis
        
        undergone intravasation
        
        established secondary areas of growth