Transcription Flashcards
Transcription basic overview
Transcription is the first stage of protein synthesis. It requires the synthesis of an mRNA strand from a section of DNA.
Start and end of Transcription
Transcription of a gene starts from a region
of DNA known as the promoter and ends at a DNA sequence known as the terminator.
Enzyme used in transcription and its function
RNA polymerase enzyme is responsible for transcription.
It binds at the promoter and moves along DNA to unwind the double helix. It also breaks the hydrogen bonds between the bases separating the DNA strands. RNA nucleotides can then align with their complementary base partner on the template strand and form a primary transcript of mRNA.
Stages of transcription for extended answers 1.
The DNA unwinds as the RNA polymerase moves along a section that codes for a protein.
Stages of transcription for extended answers 2.
The DNA molecule ‘unzips’ when hydrogen bonds are broken, separating the two strands.
Stages of transcription for extended answers 3.
Bases on the DNA strand are exposed.
Stages of transcription for extended answers 4.
mRNA nucleotides move in and form complementary base pairs with one of the DNA strands (the coding strand), according to the base pair rule:
RNA nucleotides are added at a 3′ growing tip, elongating the mRNA until the terminator sequence on the DNA is reached.
Stages of transcription for extended answers 5.
Strong chemical bonds form between the phosphate of one nucleotide and the ribose sugar of the next, building a primary transcript of mRNA.
Stages of transcription for extended answers 6.
The weak hydrogen bonds that were holding the DNA and mRNA strands together break allowing the mRNA primary transcript to leave the nucleus and enter the cytoplasm.
Stages of transcription for extended answers 7.
Hydrogen bonds reform between the 2 DNA strands, and the DNA molecule rewinds to form a double helix.
