Introduction on Cell Cycle Distinction between Living and Non-Living matters Living things reproduce and they have a capacity to procreate Procreation in the living organism has a cellular basis A great German Physician – Rudolf Virchow put this distinction very brilliantly – Where a cell exists, there must have been a preexisting Cell, just as the animal arises only from an animal and the plant only from a plant
Lecture Delivered at KMC – IC3 October 2011
Format of LectureIntroduction on Cell CycleConcept of Cell DivisionTypes of Cell DivisionRole of Chromosomes in Cell DivisionMitosis: Technical CharacteristicsMeiosis: Technical CharacteristicsOverall Learning Outcome
Introduction on Cell CycleDistinction between Living and Non-Living
mattersLiving things reproduce and they have a capacity
to procreateProcreation in the living organism has a cellular
basisA great German Physician – Rudolf Virchow put
this distinction very brilliantly – Where a cell exists, there must have been a preexisting Cell, just as the animal arises only from an animal and the plant only from a plant
Continued:Rudolf Virchow (1821 – 1902) explained this
concept of cell cycle by using a Latin axiom “Omnis cellula e cellula” – meaning every cell from a cell.
The continuity of life is based on the reproduction of cells – cell division
Virchow extended his argument on the basis of the existing cell theory proposed by Schleiden and Schwann
Postulates of Cell CycleAll living organisms are composed of cells
and cell productsThere are considerable similarities in the
chemical constitution and metabolic activities of all cells
The total activities of an organism is the sum of the activities and interactions of its independent cell units
Structural Types of CellProkaryotic Cell Eukaryotic Cell----- Prokaryotic Cell – Greek word combination of
the word Pro means first and Karyon means nucleus. The Prokaryotic cells are in the form of bacteria and blue green algae. These are very small and show primitively organised nucleus and cytoplasm
----- Eukaryotic Cell – Greek word combination of the word Eu means true and Karyon means nucleus. The Eukaryotic cells are found in the most of the algae, fungi, plants and animals.
Difference Between Prokaryotic and Eukaryotic CellsProkaryotic Cella)Nuclear membrane
absentb)Nucleolus absent c)Lack of clearly
defined membranesd)Mitotic apparatus
absente)Nucleus diffused or
Eukaryotic Cella)Nuclear membrane
is presentb)Nucleolus is also
made up of DNAd)Mitotic apparatus
presente)Nucleus is well
Biological Organisation of ProtoplasmProtoplasm is bounded by a cell membrane. It is
further divisible into cytoplasm and nucleoplasmNucleoplasm is enclosed by the nuclear
membraneThe protoplasm is highly organised and it consists
of a number of organelles which are highly ordered structures performing various functions
The Protoplasm also contains a number of depositions called deutoplasmic substances and vacuoles
Concept and Key Roles of Cell DivisionCell Division plays several important roles in
the life of an organismTo explain this – one can take an example of
amoeba – because it is a unicellular organism and when it divides and forms duplicate offsprings - the division of one cell reproduces an entire organism
Cell division is a dynamic process by which cells multiply in number leading to the production of new cells.
material to daughter cellsUnderstanding of the cellular mechanics of
cell division is very essential for a scholar
Continued:Knowledge on the molecular control systems
that regulates progress through the cell cycle will also be necessary
What happens when the control system malfunctions will also be useful to understand.
Relevance of Cell Cycle regulation – an active area of research across the globe.
Role of Chromosomes in Cell DivisionA chromosome is a body having special
organisation, individuality and functional qualitiesIt is capable of reproducing itself through
successive cell divisionsThere are two basic types of chromosomes found
in living organisms - a) those found in Prokaryotes – single circular DNA not associated with basic protein (histone); b) true chromosomes characteristics of eukaryotes, this contains DNA, RNA associated with histones and other proteins
ChromosomesThe chromosomes exhibit great variations in
their shape, number and length.The shape of the chromosomes depends on the
location of the centromere – the centromere is the driver of the chromosome because it is responsible for the movement of chromosomes in mitotic spindle.
The longitudinal half of chromosome is known as Chromatid.
The backbone of the chromosomal fibre is made up of DNA molecule