Molecular Biology; 4

The Genetic code and Transcription

Codon: A sequence of three adjacent nucleotides constituting the genetic code that determines the insertion of a specific amino acid in a polypeptide chain during protein synthesis or the signal to initiate or stop protein synthesis.

Genetic code is;

-linear

-unambiguous= each triplet specifies only a single amino acid

-degenerate=an amino acid can be coded for my more than one triplet code

-universal=the same amino acids produced in all organisms

Open reading frame (ORF): Sequence of nucleotides in DNA that contains no termination codons and can potentially translate as a polypeptide chain.

Genes that encode proteins are identified by searching the nucleotide sequence for open reading frames (ORFs) that begin with a  translation initiation codon  (ATG) and end with a translation termination codon, TAA, TAG, or TGA. 

Genes have several cis-regulatory sequences that control transcription, including promoters, silencers and enhancers.

PROMOTERS- nucleotide sequences that serve as recognition sites for the transcription machinery. They are located immediately adjacent to the genes they regulate. The core promoter consists of the TATA box…