Sunday, October 9, 2011

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Molecular biology - central dogma

The central dogma for molecular biology refers to the flow of information from DNA to RNA to proteins.

Nucleic acids are required for the storage and expression of genetic information. There are two chemically distinct types of nucleic acids:
1) deoxyribonucleic acid (DNA) and
2) ribonucleic acid (RNA).

DNA is the store of genetic information and is present not only in chromosomes in the nucleus of eukaryotic organisms, but also in mitochondria and the chloroplasts of plants. Prokaryotic cells, which lack nuclei, have a single chromosome, but may also contain nonchromosomal DNA in the form of plasmids.

The genetic information found in DNA is copied and transmitted to daughter cells through DNA replication. The DNA contained in a fertilized egg encodes the information that directs the development of an organism. This development may involve the production of billions of cells. Each cell is specialized, expressing only those functions that are required for it to perform its role in maintaining the organism. Therefore, DNA must be able to not only replicate precisely each time a cell divides, but also to have the information that it contains be selectively expressed.

Transcription (RNA synthesis) is the first stage in the expression of genetic information. Next, the code contained in the nucleotide sequence of messenger RNA molecules is translated. There is protein synthesis and thus completing gene expression.


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