Brent Cornell

    
A gene is a sequence of DNA which is transcribed into RNA and contains three main parts:

Promoter

• The non-coding sequence responsible for the initiation of transcription
• The core promoter is typically located immediately upstream of the gene’s coding sequence
• The promoter functions as a binding site for RNA polymerase (the enzyme responsible for transcription)
• The binding of RNA polymerase to the promoter is mediated and controlled by an array of transcription factors in eukaryotes
• These transcription factors bind to either proximal control elements (near the promoter) or distal control elements (at a distance)

Coding Sequence

• After RNA polymerase has bound to the promoter, it causes the DNA strands to unwind and separate
• The region of DNA that is transcribed by RNA polymerase is called the coding sequence

Terminator

• RNA polymerase will continue to transcribe the DNA until it reaches a terminator sequence
• The mechanism for transcriptional termination differs between prokaryotes and eukaryotes

Sections of a Gene

Antisense vs Sense

A gene (DNA) consists of two polynucleotide strands, but only one is transcribed into RNA

• The antisense strand is the strand that is transcribed into RNA
  • Its sequence is complementary to the RNA sequence and will be the "DNA version” of the tRNA anticodon sequence
  • The antisense strand is also referred to as the template strand
• The sense strand is the strand that is not transcribed into RNA
  • Its sequence will be the “DNA version” of the RNA sequence (i.e. identical except for T instead of U)
  • The sense strand is also referred to as the coding strand (because it is a DNA copy of the RNA sequence)

Either of the 2 polynucleotide strands may contain a gene, and hence the determination of sense and antisense is gene specific

Antisense vs Sense Strands