The Mitotic Cell Cycle
chromosomes
structure of chromosomes
threads of nucleoprotein particles seen inside the nucleus of a plant or an animal cell
these threads have the ability to carry out self replicating
so they have a specific organisation and individuality
they serve as the physical carriers of genes/genetic information fm one generation to another
genes - hereditary units
composition of chromosomes
nucleic acids
dna
rna
proteins
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
complex proteins that function as enzymes
dna polymerase or rna polymerase
organic substances
phosphoric acid group, etc
inorganic salts
extremely complex
1897 - seen in the form of very fine threads
called it chromatin
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
number
varies fm organism to organism
in humans - 23 pairs - continues in all species
can be diploid or haploid
two sets - diploid
chromosomal number (46 - sets of chromosomes) represented in two sets or one set
like gametes have only half the number
diploid number is '2n'
haploid number is 'n'
number of chromosomes - 23
banding pattern determines ancestry
size
measured in micrometers - µm
varies - fm small 0.2 µm - larger 50 µm
plant's ones are larger than animal's ones
monocot's ones are larger than dicot's ones
morphology of chromosomes
study of external features- shape and structure
2 phases of cell division - interphase and dividing (metaphase)
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
entire surface is intensely stained except one portion - narrow, less-stained region along entire length of chromosome, don't take up stains as well
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
- chromosomes
best to study in the metaphase/anaphase
in the interphase - extremely thin and thread like - hard to see
shape and size changes through the stages
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
important function
divides the chromosomes into 2 parts on 2 sides - chromatids
divided into the arms - chromatin threads
centromere position - method used to identify evolution changes across species
nucleation polymerization of tubulin protein to make microtubules
region where the attachment of spindle fibres take place
types of chromosomes
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
location
nuclear
extranuclear
seen in autonomous organelles which have their own chromosomes - mitochondria, chloroplasts, etc
isobrachial
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
centromere is not terminal - sub terminal having two chromatins - one chromatin is very long, other is very short
acrocentric/ j-shaped chromosomes
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
sub-metacentric
one is longer, other is verryy small
secondary constriction/ nor - nucleolar organiser region
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
tertiary
its position is also constant - can be used to study evolutionary relationship
telomeres
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
provide stability to the chromosome
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
if few junk ones are lost its okay, since the actual important info isn't getting lost
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
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
satellites
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
centromere, telomere, chromosomes satellites
cell cycle
orderly sequence of events that takes place between 2 cell divisions
sequence of events by a which a cell will grow
duplicate its genome, synythesis all its requirements, and then divide to form daughter cells
phases
interphase
m phase, mitotic phase/ karyokinesis - division of nucleus
cytokinesis
duration can vary
divides at end of every hour in humans
some 20 mins
depends on type of cell
external factors like temperature and food availability
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)
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
3 options now
cell continues participate and undergo division
get arrested at any point and
go into G0 phase (opt out of cell cycle)
G0 phase
not all cells divide - neurons, RBCs, cells in skeletal system
non cycling phase of cell cycle
reason
certain proteins force them into cell cycle - cycling factors
deactivating cycling factors
some genes activate the differentiating factor to make it go into G0 phase
cells are relatively dormant - quiescent
dont metabolise till they get a signal fm outside
can rapidly divide though
can't go back to g1 phase
replication of dna
denaturation - h bonds between bases broken - polynucleotide chains broken
AT bases - 2 hydrogen bonds
GC bases - 3 hydrogen bonds
semi-conservative mechanism - only 1 strand conserved
1 original strand
only 2 chromatids before
tetrad - 4 chromatids - replicates
dna is doubled
2 sister chromatids
bivalent
6-8 hours
no options for the s phase
increase in size of cell, and number of energy molecules (atp, energy-rich nucleotides) increase
RNA
diff fm g1 coz of active rna synthesis
R RNA
ribosomal rna
M RNA
messenger rna
N RNA
nucleolar rna
organelles
synthesised semi autonomous
protein
protein buildup in cell - diff kinds of proteins
formation of asters
formed by polymerisation of tubulin
microtubules
condensating
helps in condensation of chromosomes (chromatin-> chromosomes)
DNA
dna content again doubles - double of s, which is double of g1
g1 - remains same
s - doubles
g2 - doubles again
4x more
2-5 hrs
mitotic phase
m phase
the actual dividing phase
karyokinesis - splitting of nucleus
after cytokinesis
diff parts
separation of chromatins, and redistribution of daughter into daughter cells
division of cytoplasm - daughter cells
prophase, prometaphase, metaphase, anaphase, telophase
in cell - spindle apparatus with centre and poles
centromere is in the centre
so there is only one long end, since the centromere is at the extreme end
2a. cell cycle
nucleosome - the complex of histones
upper arms of chromosomes - p arms, lower, shorter - q arms
packaging of dna
double helix dna is related to histone proteins
dna wraps and coils very tightly around histones
forming chromatin fibre
which finally forms chromosomes
1 chromosome has several thousand genes
gene
segment of dna that codes for a protein
locus/ loci
position of a gene in a chromosome
homologus
pair of chromosome
allele
2 genes for same feature, but one dominant, 1 recessive
different forms of one gene
for same species, genes are on the same chromosome and loci
pairs of chromosomes found in diploid cells
1 maternal 1 paternal
similar centromere position
similar chromosome size and shape
same genes different alleles
sister chromatids - duplicated dna
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
karyogram
pictorial representation of all chromosomes in a cell
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
24 hours
prophase
sometimes prometaphase
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
primary constriction is called the centromere
p arm - short, q arm - longer
later breaks into 2 for the 2 new daughter cells
metaphase
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
so the cleavage furrow deepens/ constricts, becomes so deep that mature mother cell divides (pinches off) into 2 daughter cells
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
like band of microfilaments, golgi bodies area used in equatorial region (where cell plate forms)
indicated (represented) by middle lamella (it forms the middle lamella between adjacent/split/newly divided cells)
specialised organelles associated with secretion
secretes vesicles
accumulate in equatorial region (centre/ equator)
as vesicles increase, they fuse together
fusing contributes to formation of cell plate, forming 2 adjacent daughter cells
not necessary that all vesicles fuse completely
some places where the vesicles don't fuse
zone of continuity
between 2 plant cells
called plasmodesmata
tiny gaps through which strands of cytoplasm run through
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
not in plants
microfilaments/ contractile ring in animal cells/ cleavage furrow
no microfilaments - golgi vesicles used
formation of cell plate
in plants
not in animals
cell wall
only in plants
not in animals
significance of mitosis
important functions
for growth
only somatic cells - mitotic
anything to do with growth and evelopment of cells - directly linked to mitosis
in animals - continuous process
each part grows
different for plants
growth is concentrate in tip of root and shoot
because of meristramatic tissues
germ cells is meiosis
cell size
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
stability
genetic stability
maintainenace of chromosomal number
meiosis also
repair
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
reproduction
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
ancestry
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
immunity
2 types of lymphocytes
B and T
they divide by mitosis
role in decidint immune response
form clones by mitosis
stem cells
definition
a unique group of undifferentiated and unspecialised cells
makes them unique-retain their ability to undergo indefinite mitotic division
when they undergo indefinite mitotic division
they can form clones (self replication or self-renewal)
also get differentiated to form many idfferent functions
characteristics
aka progenitor cells
parents, ancenstor, mother of all cells
can give rise to different cells
can self replicate/renewal
capable of multi-lineage differentiatoin
form different types of cells fm different lines
form differnet cells
can be used for tratment of malignant and non malig diseases
find a possible cure
eg leukemia, parkinsons
like blood cells or neural cells - for parkinsons
haemotopoietic stem cells and neurogenic stem cells
potency of stem cells
definition
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
types - 5
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)
formed in initial stages of division
blastula
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
- significance of mitosis
- stem cells
2b. packaging of dna - ms simi
gastrula
embryo
foetus
formed fm the 16th cell stage (morula)
multipotent
oligopotent
unipotent
descendant of totipotent
inner cell mass - blastomeres
ectoderm
mesoderm
endoderm
harvested fm blastomeres, the inner cell mass and 3 inner germ layers
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
oligo meaning 'few'
can give rise to few other types of cells
eg
lymphoid stem cells
myeloid stem cells
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
can only divide and give rise to muscle cells for self-renewal
the only one that can do self-renewal
but fm different families
need for stem cells
5 reasons
important for repair, regeneration and recovery of
depending on physiological needs of cells
capable of adapting themselves to different needs
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
to different physiological conditions
based on source fm where stem cells are obtained
3 types
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
click to edit
source
fm bone marrow of large bones
fm amniotic fluid
click to edit
nomenclature
adult stem cells are named based on tissues
treatment
important
when injurgy to spinal cord
liver sclerosis
degenerative diseases of spinal cord
stem cell therapy
use of stem cells to either prevent disease or treat
combined immunodeficiency diseases - CID
multiple organ failures
scid - severe
blood cancers
leukemia - blood
lymphoma
haemapoietic stem cells used to treat
lymphoid
disorder
born with
sickle cell anaemia
congenital disorders
thalassmia
decrease in haemoglob count
augmentation
subjected to chemo, reduction in amount of bone marrow
increase no./amount of bone marrow
to treat auto-immune disorders
when body produces antibodies against own organs
eg
diabetes
parkinsons
cancer biology
plaeripotent
general description
cell division is very important
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
uncontrolled, unschedules proliferation and spread of abnormal cells
cancer
a cancer cell survives at the expense of normal cells
aka neoplastic (abnormal) cells
tumour
an undifferentiated mass of tissues which is formed by uncontrolled division of cells
all cancers are tumurous
it is the spread of abnormal cells
not all tumours are cancerous
when a group of cells begins to spread
examples
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
carcinogens
process by which normal cells (proto-oncogen) gets converted into a cancerous (malignant/ oncogen) - carcinogenesis
agents which cause carginogenesis are called carcinogen
types of cancer - manifestation - where it occurs
4
carcinoma
90% of cancers
cancer of epithelial cells
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
lymphomia
cancer of blood cells
rbcs or wbcs
8%
cancer of cells of immune system - b and t lymphocytes
types of cancer on the basis of nature of cancerous cells
2
benign
localised
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
so can be treated
call them tumours not cancers (not malignant) since they are not differentiated cells
malignant
still dangerous
since some can get converted into 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
metastasis
90% deaths of cancer
unique
establishing secondary area of growwth
angelina jolie
caused by mutations
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
malignant - capable of spreading
non cancerous
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
benign no latent period
for malignant there is a period
since capsule
period of time between exposure to initiator and progression of disease cancer
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
with charcoal in it
hold the charcoal on themselves to keep warm
irritation fm charcoal + heat - causes skin cancer
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 human
pappiloma
epstein bar
hpv
herpes simplex type 2
hereditary
high incidents of certain cancers
inheritance of gene that results in cancer
genetic presisposition
can be dominant or recessive
characteristics of cancerous cells
unique properties which the bodies can't control
unorganised growth
when a normal cell grows, it recieves a signal fm ourside - signalling
cancer generated own growth signals
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
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
stop
failure to respond to stop signals
2 adjacent cells
cell membranes in contact
respect each others space
but cancerous cell grows over and above the cell it comes in contant with
no contact inhibition
don't grow over each other
stop when they touch each other
division
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
apoptosis
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
in chemo, induces cancer cells to die
because of telomerases
angiogenesis
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
uses up all o2 and blood vessles cpme
metastasis
grow on others/surrounding cells
positive feedback
more cancer, more o2 used
this property make it neoplastic
centrifugal - since cell plate forms from centre (equatorial region of cell) and moves to periphery of cell
- cancer biology
spindle fibres just starting to move
in prometa - they have moved to poles
arranging
chromosomes get arranged in the equatorial region
spidle fibres get sttached to all the chromosomes
organisation phase
centrosomes reach opposite poes
spindle fibres are fully formed
chromosomes line up at the metaphase plate/ equator
anaphase
centromere of each chromosome divides
sister chromatids split at the centromere
spindle microtubules shorten
chromatids pulls to opposite poles
shortest phase
longest phase
telophase
nucleolus forms again - 2 formed at each pole
hydrolysation of chromosomes to form
chromatids reach the poles
chromosomes decondense, become long and thin
nucleolus forms
nuclear envelope reassembles
spindle fibres break down
cytokinesis starts
steps in metastasis
ability to establish areas of secondary growth
what kills the patient - growing over other cells
3 steps
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
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
- and prevents the wbcs fm seeing the cancer cell
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
blood has come out, so it can now establish areas of secondary growth
targets the organs that are have complementary addition molecules to its ones
volume of the cell breaks open and internal bleeding happens
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
cancer associated genes
4 types of genes
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
initially a protoonco
tumour supressor
different stages
sex hormones, steroids, etc
remains active only in a non dividing cell
exposure to carcinogen/ mutation
starts stimulating production of tmumuour cells/ new types of cacners
supposed to fight the tumour, but instead it promotes the tumour
for growth and repair of damaged and degenerated parts
- characteristics
cancerous cells form
- general description
types of cancer - manifestation - where it occurs
types of cancer on the basis of nature of cancerous cells
cancer associated genes
steps in metastasis
most common
forms of carcinogens
which get nourishment fm the blood
perfect disguise - seen as 'self'
internal bleeding is a symptom of cancer
since all the nutritious blood is now everywhere
instead of supressing, it promotes
viral oncogens
diff kinds of viruses
epstein bar virus - ebv
human pappiloma virus - hpv
herpes simplex type 2 virus -
causes lymphoma cancer
causes cervical cancer
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
stages of cancer
4
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
cancer wouldn't develop as fast then
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
inside the nucleus of eukaryot
it hasn't replicated or divided yet
or
don't divide - they get differentiated to get specialised
these ones enter into g0 phase
doubt
doubt - how still divide?
just dormant, not dividing till signal but still can divide?
doubt - what?
colour
chromosomes attached to spindle fibres at centromere/ kinetochore
with centromeres leading towards poles
opposite of prophase
doubt - only?
stages of cancer
word - order
can form tumours
doubt/word - is it a tumour?