center Genotype and Phenotype

- Getting Started -

Getting Started
The process of transcription ...
... is catalyzed by a multisubunit enzyme called RNA polymerase, which needs as substrates double stranded DNA, and the ribonucleotides ATP, UTP, CTP and GTP.

One at a time, this enzyme adds ribonucleotides to a growing RNA strand by joining incoming ribonucleotide triphosphates to the ribose sugar molecule of the last nucleotide of the growing RNA strand. Two of the phosphate groups are removed from the triphosphate and a covalent bond is formed between the remaining phosphate and the third carbon atom of the ribose sugar at the end of the RNA strand.

Initiation of the transcription process begins with binding of the RNA polymerase enzyme to the DNA molecule at a region known as the promotor site. This site is right in front of a gene where transcription will begin. In bacteria, this region contains two short sequences of bases that appear to be the same in all, or most, promotors.

The RNA polymerase enzyme does not copy the promotor into the RNA, but begins the synthesis of the RNA at a specific nucleotide sequence called the start signal or initiation site which is often the bases GTA on the DNA (which then become the bases CAU on the RNA molecule).

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Science at a Distance
© 1997, 1998, 1999, 2000 Professor John Blamire