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Flashcards in 7.3 Transcription Deck (5)
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State the direction in which transcription occurs

Transcription occur in a 5'-3' direction


Outline the features of the antisense strand

• Transcribed into RNA
• Carries the complementary version of the genetic code
• Its sequence will be complementary to the RNA sequence and will be the "DNA version" of the tRNA anticodon sequence


Outline the features of the sense strand

• Not transcribed into RNA
• Contains the genetic code
• Its sequence will be the "DNA version" of the RNA sequence (identical except for T instead of U)


Explain the process of transcription in prokaryotes

1. Transcription begins at a promoter region: a short series of bases which are not transcribed, but allow RNA polymerase to attach and determine which is the antisense strand.
2. RNA polymerase adds nucleoside triphosphates complementary to the antisense strand to create a chain in the 5'-3' direction, forming phosphodiester bonds between the nucleosides. As triphosphates are added, 2 phosphates are released creating RNA nucleotides, which form the mRNA strand.
3. Transcription is stopped by a terminator sequence, a sequence of bases on the antisense DNA strand that when transcribed cause RNA polymerase to detach from DNA, ending the transcription process.


Outline why and how mature mRNA is formed

Sections of the mRNA strand called introns (interrupting sequences) carry a base sequence not required for translation. These introns are spliced out, leaving only exons (expressed sequences). Exons are joined to form a mature mRNA strand, carrying the mRNA version of the gene's base sequence.