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

INTRODUCTIONINTRODUCTION

• 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.

• 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.

The Cell Cycle 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.

• G1 stage : Growth & development of the cell, Protein synthesis

• S-phase : Chromosome replication viaDNA synthesis

• G2 stage : Growth & developmentOrganelle Replication

• G1 stage : Growth & development of the cell, Protein synthesis

• S-phase : Chromosome replication viaDNA synthesis

• G2 stage : Growth & developmentOrganelle Replication

DNA Replication

Chromosome Replication & Division 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

The Mitotic cell cycle is essential to cell division and growth of an

organism

The Mitotic cell cycle is essential to cell division and growth of an

organism

Gene Expression and Cell Division conflict:Gene Expression and Cell Division conflict:

Gene expression requires that chromosomal DNA be uncoiled to allow access to enzymes such as RNA polymerase

Gene expression requires that chromosomal DNA be uncoiled to allow access to enzymes such as RNA polymerase

Cell division requires that chromosomes be tightly coiled to allow orderly migration of chromosomes to daughter cells

Cell division requires that chromosomes be tightly coiled to allow orderly migration of chromosomes to daughter cells

☺☺

☺☺

Gene Expression and Cell Division are separated into different stages

Mitosis Mitosis

Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase.

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. Mitosis deals only with the segregation of the chromosomes and organelles into daughter cells.

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).

WILL BE CONTINUED…..