Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Cell Cycle Lecture PPT
RNA.
? RNA is polymer of ribonucleotides.
? Linked together by 3'-5' phosphodiester bond.
? Function of RNA-
? Protein synthesis.
? Genetic material.
? Ribozymes.
?
TYPES OF RNA.
? Messenger RNA
mRNA
? m RNA
? Transfer RNA
t RNA
? T RNA
? Ribosomal RNA
r RNA
? R RNA
GENE REGULATION.
? Gene regulation refers to the mechanism that act to induce or
repress the expression of a gene.
Level of Gene control.
? Gene on DNA
? |
? - -Transcriptional control
?
? Primary transcript
?
? ( RNA processing control)
m RNA
( RNA transport control )
| -- Translation control.
Protein
TYPES OF RNA.
m ? RNA- messenger.
Translation.
r-RNA- ribosomal
Protein synthesis.
t- RNA- transfer
translation
Sn-RNA-- small nuclear
m RNA processing poly a addition
Sno-RNA---small nucleolar
r- RNA processing/ maturation,
methylation.
Regulatory RNA---siRNA and miRNA
Regulation of transcription and translation.
Regulatory RNAs.
? Small nuclear RNA
Sn RNA
? Sn RNA
? micro
mi RNA
? RNA
? Small interferring
Si RNA
? RNA
REGULATORY RNA.
? Inhibition of gene expression.
siRNA
? Inhibition of gene expression.
mi RNA
? Tumour suppression and oncogenes.
? Primary transcript RNA.
Nascent RNA ? Needs to be processed like--capping, RNA splicing.
PHASE OF CELL CYCLE
? G1---- (Gap-1)--Phase.
? S-------Synthetic phase.
? G2- --- Gap-2 Phase.
? M-------Mitotic phase.
? G1, S, and G2-----Interphase--cell prepare to divide.
? M phase---Both DNA and cytoplaslm divide to produce two
daughter cells.
PHASE OF CELL CYCLE.
INTERPHASE.
INTERPHASE- G1 PHASE.
? 1st growth stage after cell division.
? Cells matures by making more cytoplasm and organelles.
? Cells carries on its normal metabolic activity.
? S-STAGE-
? synthesis stage.
? DNA is copied or replicated.
INTERPHASE --G2 - stage
? 2nd growth stage.
? Occurs after DNA has copied.
? All cell structure needed for division are made.(eg-centriole).
? Both organelles and proteins are synthesized.
? DNA replicates, centriole if present replicate.
? cell prepares for division.
MITOSIS.
MITOSIS.
? Division of nucleus also called karyokinesis.
? Has four stages.
? Four mitotic stages are--
? Prophase.
? Metaphase.
? Anaphase.
? Telophase.
?
Early prophase.
? Chromatin in nucleus condenses to form visible chromosome.
? Mitotic spindle forms.
? Late Prophase? nuclear membrane and nucleolus
are broken down.
? Chromosome condenses and clearly visible.
? Spindle fibre called kinetochore attach to the centromere of
each chromosome.
? Spindle finishes forming between the poles of the cell.
?
METAPHASE.
? Chromosomes, attached to the kinetochores fibre, move to
the centre of the cell.
? Chromosomes now lined up at the equator.
ANAPHASE --
? occurs rapidly.
? Chromatids are pulled apart to opposite poles
by kinetochores fibres.
?
TELOPHASE.
? Sister chromatids at opposite poles.
? Spindle disasembles.
? Nuclear envelope forms.
? Nucleolus reappears.
? Cytokinesis occurs.
? Chromosome reappear as chromatin.
CYTOKINESIS.
? Means division of cytoplasm.
? Division of cell into two identical half called daughter cells .
? Daughter cells of mitosis have same number of chromosomes
that of parent cell.
? Must grow in size to become mature cells.( G1 of Interphase)
METAPHASE.
ANAPHASE.
TELOPHASE.
PHASE OF CELL CYCLE AND REGULATION.
Cyclin D ,CDK-4
G2-
G1
cdk1
S ?cyclin
E,cdk2
ROLE OF CDK-1 COMLEX IN G2 CHECK POINT
REGULATION.
? CYCLIN B--CDK-P ---INACTIVE
? <- Active protein kinase <-
DNA strand break.
? |
? CYCLIN ?B CDK-1 ---ACTIVE
? |
? Phosphorylation of several protein.
? |
? Bipolar spinle formation -----MITOSIS.
Cyclin and cdk molecule.
FIVE PHAGES OF THE CELL CYCLE.
? G1--Primary growth phase.
? S---synthesis, DNA replicated.
? G2--secondary growth phase.
? Collectively these 3 stages are called interphase.
? M--mitosis.
? C--cytokinesis.
CELL CYCLE REGULATION.
? Why cell cycle cycle regulation-------
? cell division is expensive process.
? Maintain integrity of genome.
? Proper cellular homeostasis.
? Prevent onset of mutation.
KEY REGULATOR.
Cdk/cyclin dependent protein,catalytic protein.
? Cyclin, regulatory protein.
Apart from these , two other important regulator....
? (Rb protein and p53 protein.)-Tumours suppressor protein.
Oncogenes also disrupt cell cycle.
? P53 is a tumor suppressor gene ?
? p53 gene produces a protein with a
molecule mass of 53kDa.This protein suppresses the tumour
formation. it arrest the cell cycle at G2/M check point.
Mutation in p53 gene are found in 50% of all cancer.
? It distrupts cell cycle both at G1/S and G2/M check point by
coding for a CDK inhibitors called p21 which binds to several
cyclin CDK comlexes influencing the cell cycle.
BCL2 GENE.
? BCL2 gene associated with beta ? cell lymphoma appears to
induce cyclin D gene. Excess cyclin D expression could result in
unrestained cell division leading to cancer.
? CDK INHIBITORS----------
? CDK are inhibited by CDK inhibitors
which are produced in response to signal like DNA damage.
These inhibitor lead to arrest of cell cycle.
CYCLINS.
? They named because they undergo a cycle of synthesis of
degradation in each cycle.
? It is a regulatory protein of cell cycle and shows continuous
rise and fall during the various stages of cell cycle.
? Synthesis of cyclins proteins begins during G1 phase and they
increases their concentration till Metaphases but in anaphase
they are degraded by the actvated by the actIvity of APC.
FOUR CLASSES OF CYCLINS.
? G1 CYCLINS---
? Help to promote passes through " start" .
? G1/S CYCLINS----
? Bind to Cdks at the end of G1 and commit cell to
DNA replication.
? S-CYCLINS----
? Bind Cdks durindg S phase cand are required for
initiator of DNA replication.
? M CYCLINS --Promote the event of mitosis.
Cyclin.
Cyclin is the important key regulator of cell cycle.
? Cyclin...........
Also regulate the activity of cdk.(cyclin dependent kinase.)
? Regulator of both cell cycle and cdk.
CYCLIN DEPENDENT KINASE.
? Progression of cell cycle is controlled by a conserved
set of protein called --
KINASE
? KINASE.
? Regulate the progression of cell cycle in association
with another group of protein called as--
CDK
? Cyclins.
? Concentration of cyclins fluctuates throughout the
cell cycle
CYCLINS
? Cyclins.
DIFFERENT TYPES OF Cdk.
? G2 to M phase.
Cdk1 ? G2 to M
? G1 to S.
Cdk2 ? G1 to S phase.
? G1 to S.
? Gap 1 to Synthetic phase.
cdk4
Cdk 20--Metaphase to Anaphase....
THREE MAIN TRANSITION CHECK POINTS IN
CELL CYCLE.
G1 TO S.
G2 TO M.
METAPHASE
TO ANAPHASE.
G1 CHECK POINT.
Checks conditions are favouring
for cell division.
Checks for genomic DNA damage
at G1,adequate energy reserves,
DNA damage.
Synthesis of G1 cyclins must
reach specific level to cross the
start point.
Rb protein.(Retinoblastoma protein).
? Classic tumour suoppressor.
? Its product called Rb protein prevents the cell to migrate from
G1 to S Phase.
? Master regulator of biological pathway like---
? Cell Growth, cell cycle checkpoints, differentiation,
replication, genomic stability and apoptosis.
P53 protein.
(GUARDIAN OF GENOME.)
? Tumour suppressor gene.
P53 PROTEIN.
? P53.
? Preventing tumour developement
P53
? p53
? Inhibit over expression of cell.
P53
? Regulate the cell cycle.
This post was last modified on 30 November 2021