Lesson 4A: Protein Synthesis: Transcription Flashcards
Gene Expression
The process of transferring genetic material from DNA into a protein
Two processes involved:
1. Transcription
2. Translation
Gene
a segment of DNA that controls the production of a protein
Transcription
Copying the info of a segment of DNA (a single gene referred to as the transcription unit) onto a mRNA molecule that can be used in the cytoplasm
—> occurs in 4 stages
Transcription step 1: Initiation p1
Transcription factors bind to the TATA box in the promoter region located just before the gene to be transcribed (transcription unit), RNA polymerase recognizes the promoter region and binds to the Transcription factors forming a transcription complex
Transcription step 1: Initiation p 2
RNA polymerase will bind to one strand of the double stranded DNA
— this strand is called the template or anti-sense strand; is transcribed
— the other strand is called the coding/sense strand and is not transcribed BUT it will have the same vase sequence as the RNA
Transcription step 2: Elongation
RNA polymerase will then synthesize a series of complimentary strand of mRNA
—RNA Polymerase reads the FNA in the 3’ to 5’ direction; creates the mRNA 5’ to 3’ direction
Transcription step 2: Elongation pt 2
RNA polymerase moves along the reading frame of the DNA template reading 3 bases at a time and adding RNA nucleotides to the growing mRNA molecule. As said molecule grows it peels away from the DNA template strand and the DNA recoils behind it.
—mRNA will always start with the sequence AUG
Transcription step 3: Termination
Transcription will continue until the RNA polymerase reaches a ‘termination site’ on the DNA
Transcription step 4: mRNA processing
-A special nucleotide sequence is added to both ends of the new mRNA
-A complex of enzymes and nucleic acids cut out all of the introns and joins the end of the exons
-The finished mRNA is then transported from the nucleus into the cytoplasm
