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The Cell Theory is one of the foundations of modern biology :

INTRODUCTION. The Cell Theory is one of the foundations of modern biology :. All living things are composed of one or more cells; The chemical reactions of living cells take place within cells; All cells originate from pre-existing cells; and

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The Cell Theory is one of the foundations of modern biology :

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  1. INTRODUCTION The Cell Theory is one of the foundations of modern biology : • All living things are composed of one or more cells; • The chemical reactions of living cells take place within cells; • All cells originate from pre-existing cells; and • Cells contain hereditary information, which is passed from one generation to another.

  2. The Cell Cycle Stages of the cell cycle The cell cycle is an ordered set of events, culminating in cell growth and division into two daughter cells. Non-dividing cells not considered to be in the cell cycle. The stages, pictured to the above, are G1-S-G2-M. The G1 stage stands for "GAP 1". The S stage stands for "Synthesis". This is the stage when DNA replication occurs. The G2 stage stands for "GAP 2". The M stage stands for "mitosis", and is when nuclear (chromosomes separate) and cytoplasmic (cytokinesis) division occur.

  3. G1 stage : Growth & development of the cell, Protein synthesis • S-phase :Chromosome replication viaDNA synthesis • G2 stage : Growth & developmentOrganelle Replication

  4. DNA Replication

  5. Chromosome Replication & Division Every time a cell divides, each chromosome must be carefully replicated (copied) and then distributed to assure that each daughter cell gets a complete and accurate set of information. Thus, nuclear division includes successive processes of chromosome replication, separation, and distribution

  6. The Mitotic cell cycle is essentialto cell division and growth of anorganism Gene Expression and Cell Division conflict: ☺ Gene expression requires that chromosomalDNA be uncoiled to allow access to enzymessuch as RNA polymerase ☺ Cell division requires that chromosomes betightly coiled to allow orderly migration ofchromosomes to daughter cells

  7. Gene Expression and Cell Division areseparated into different stages

  8. Mitosis Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis deals only with the segregation of the chromosomes and organelles into daughter cells.

  9. The condensed replicated chromosomes have several points of interest. The kinetochore is the point where microtubules of the spindle apparatus attach. Replicated chromosomes consist of two molecules of DNA (along with their associated histone proteins) known as chromatids. The area where both chromatids are in contact with each other is known as the centromere. The kinetochores are on the outer sides of the centromere. Remember that chromosomes are condensed chromatin (DNA plus histone proteins).

  10. Will be continued…..

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