Download MBBS Cell Cycle Lecture PPT

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? Linked together by 3'-5' phosphodiester bond.
? Function of RNA-
? Protein synthesis.
? Genetic material.
? Ribozymes.

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?
TYPES OF RNA.

? Messenger RNA

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mRNA

? m RNA

? Transfer RNA

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t RNA

? T RNA

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? Ribosomal RNA

r RNA

? R RNA

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GENE REGULATION.

? Gene regulation refers to the mechanism that act to induce or

repress the expression of a gene.

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Level of Gene control.

? Gene on DNA
? |
? - -Transcriptional control

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?
? Primary transcript
?
? ( RNA processing control)

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m RNA

( RNA transport control )

| -- Translation control.

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Protein


TYPES OF RNA.

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m ? RNA- messenger.

Translation.

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r-RNA- ribosomal

Protein synthesis.

t- RNA- transfer

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translation

Sn-RNA-- small nuclear

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m RNA processing poly a addition

Sno-RNA---small nucleolar

r- RNA processing/ maturation,

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methylation.

Regulatory RNA---siRNA and miRNA

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Regulation of transcription and translation.
Regulatory RNAs.

? Small nuclear RNA

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Sn RNA

? Sn RNA

? micro

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mi RNA

? RNA

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? Small interferring

Si RNA

? RNA

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REGULATORY RNA.

? Inhibition of gene expression.

siRNA

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? Inhibition of gene expression.

mi RNA

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? Tumour suppression and oncogenes.

? Primary transcript RNA.

Nascent RNA ? Needs to be processed like--capping, RNA splicing.

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PHASE OF CELL CYCLE

? G1---- (Gap-1)--Phase.
? S-------Synthetic phase.
? G2- --- Gap-2 Phase.

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? M-------Mitotic phase.
? G1, S, and G2-----Interphase--cell prepare to divide.
? M phase---Both DNA and cytoplaslm divide to produce two

daughter cells.

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PHASE OF CELL CYCLE.
INTERPHASE.
INTERPHASE- G1 PHASE.

? 1st growth stage after cell division.

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? Cells matures by making more cytoplasm and organelles.

? Cells carries on its normal metabolic activity.
? S-STAGE-
? synthesis stage.

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? DNA is copied or replicated.
INTERPHASE --G2 - stage

? 2nd growth stage.
? Occurs after DNA has copied.

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? 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.

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MITOSIS.

? Division of nucleus also called karyokinesis.
? Has four stages.
? Four mitotic stages are--

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? Prophase.
? Metaphase.
? Anaphase.
? Telophase.
?

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Early prophase.

? Chromatin in nucleus condenses to form visible chromosome.
? Mitotic spindle forms.
? Late Prophase? nuclear membrane and nucleolus

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are broken down.

? Chromosome condenses and clearly visible.
? Spindle fibre called kinetochore attach to the centromere of

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each chromosome.

? Spindle finishes forming between the poles of the cell.
?

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METAPHASE.

? Chromosomes, attached to the kinetochores fibre, move to

the centre of the cell.

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? Chromosomes now lined up at the equator.

ANAPHASE --

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? occurs rapidly.
? Chromatids are pulled apart to opposite poles

by kinetochores fibres.

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?

TELOPHASE.

? Sister chromatids at opposite poles.

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? Spindle disasembles.
? Nuclear envelope forms.
? Nucleolus reappears.
? Cytokinesis occurs.
? Chromosome reappear as chromatin.

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CYTOKINESIS.

? Means division of cytoplasm.
? Division of cell into two identical half called daughter cells .

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? Daughter cells of mitosis have same number of chromosomes

that of parent cell.

? Must grow in size to become mature cells.( G1 of Interphase)

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METAPHASE.
ANAPHASE.
TELOPHASE.
PHASE OF CELL CYCLE AND REGULATION.

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Cyclin D ,CDK-4

G2-

G1

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cdk1

S ?cyclin

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E,cdk2
ROLE OF CDK-1 COMLEX IN G2 CHECK POINT

REGULATION.

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? CYCLIN B--CDK-P ---INACTIVE
? <- Active protein kinase <-

DNA strand break.

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? |
? CYCLIN ?B CDK-1 ---ACTIVE
? |

? Phosphorylation of several protein.

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? |
? Bipolar spinle formation -----MITOSIS.
Cyclin and cdk molecule.
FIVE PHAGES OF THE CELL CYCLE.

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? G1--Primary growth phase.
? S---synthesis, DNA replicated.
? G2--secondary growth phase.
? Collectively these 3 stages are called interphase.
? M--mitosis.

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? C--cytokinesis.
CELL CYCLE REGULATION.

? Why cell cycle cycle regulation-------
? cell division is expensive process.

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? Maintain integrity of genome.
? Proper cellular homeostasis.
? Prevent onset of mutation.
KEY REGULATOR.

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Cdk/cyclin dependent protein,catalytic protein.

? Cyclin, regulatory protein.

Apart from these , two other important regulator....

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? (Rb protein and p53 protein.)-Tumours suppressor protein.
Oncogenes also disrupt cell cycle.

? P53 is a tumor suppressor gene ?

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? 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.

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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

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coding for a CDK inhibitors called p21 which binds to several

cyclin CDK comlexes influencing the cell cycle.
BCL2 GENE.

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? 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.

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? CDK INHIBITORS----------
? CDK are inhibited by CDK inhibitors

which are produced in response to signal like DNA damage.

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These inhibitor lead to arrest of cell cycle.
CYCLINS.

? They named because they undergo a cycle of synthesis of

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degradation in each cycle.

? It is a regulatory protein of cell cycle and shows continuous

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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

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they are degraded by the actvated by the actIvity of APC.
FOUR CLASSES OF CYCLINS.

? G1 CYCLINS---

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? Help to promote passes through " start" .
? G1/S CYCLINS----
? Bind to Cdks at the end of G1 and commit cell to

DNA replication.

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? S-CYCLINS----
? Bind Cdks durindg S phase cand are required for

initiator of DNA replication.

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? M CYCLINS --Promote the event of mitosis.
Cyclin.

Cyclin is the important key regulator of cell cycle.

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? Cyclin...........

Also regulate the activity of cdk.(cyclin dependent kinase.)

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? Regulator of both cell cycle and cdk.
CYCLIN DEPENDENT KINASE.

? Progression of cell cycle is controlled by a conserved

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set of protein called --

KINASE

? KINASE.

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? Regulate the progression of cell cycle in association

with another group of protein called as--

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CDK

? Cyclins.

? Concentration of cyclins fluctuates throughout the

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cell cycle

CYCLINS

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? Cyclins.
DIFFERENT TYPES OF Cdk.

? G2 to M phase.

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Cdk1 ? G2 to M

? G1 to S.

Cdk2 ? G1 to S phase.

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? G1 to S.
? Gap 1 to Synthetic phase.

cdk4

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Cdk 20--Metaphase to Anaphase....
THREE MAIN TRANSITION CHECK POINTS IN

CELL CYCLE.

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G1 TO S.

G2 TO M.

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METAPHASE

TO ANAPHASE.
G1 CHECK POINT.

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Checks conditions are favouring

for cell division.

Checks for genomic DNA damage

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at G1,adequate energy reserves,

DNA damage.

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Synthesis of G1 cyclins must

reach specific level to cross the

start point.

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Rb protein.(Retinoblastoma protein).

? Classic tumour suoppressor.
? Its product called Rb protein prevents the cell to migrate from

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G1 to S Phase.

? Master regulator of biological pathway like---
? Cell Growth, cell cycle checkpoints, differentiation,

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replication, genomic stability and apoptosis.
P53 protein.

(GUARDIAN OF GENOME.)

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? Tumour suppressor gene.

P53 PROTEIN.

? P53.

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? Preventing tumour developement

P53

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? p53

? Inhibit over expression of cell.

P53

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? Regulate the cell cycle.