Transcription and translation Flashcards
What is a gene?
A length of DNA with a particular function. It makes one type of RNA and/or polypeptide.
It can become both RNA and then a protein, or just RNA.
What is a nonsense mutation?
When you replace an amino acid with a stop. The RNA transcription will not function properly.
What is transcription?
The process of turning DNA into RNA. DNA is transcribed into mRNA which ribosomes read and use to string amino acids together into a protein.
It occurs in the nucleus.
What is translation?
The process of turning RNA into protein.
It occurs in the cytoplasm.
What is the template strand?
The strand that is used as a template to make a complementary strand of RNA.
How does transcription work?
- Binds
- Unzips
- Reads
- Synthesises
- Terminates
The enzyme RNA polymerase binds to a region of DNA called a promoter sequence. This signals where transcription should begin.
RNA polymerase unzips the DNA double helix, exposing the nucleotide bases on each strand of DNA.
One strand of DNA, called the template strand, is used as a template to synthesize a complementary strand of RNA.
RNA polymerase reads the template DNA strand in the 3’ to 5’ direction and synthesizes the RNA transcript in the 5’ to 3’ direction.
RNA polymerase adds RNA nucleotides that are complementary to the template DNA strand, following base pairing rules (A pairs with U, C pairs with G).
The nucleotides bind together through phosphodiester bonds to form the growing RNA strand.
Once transcription reaches a termination sequence on the DNA, the RNA transcript is released and RNA polymerase detaches.
The result is a single-stranded messenger RNA (mRNA) molecule that corresponds to the protein-coding region of the DNA and carries the message to be translated into protein.
What is the promoter region?
The binding site for RNA polymerase that determines where transcription starts.
The - 10 box is located approximately 10 nucleotides upstream of the transcription site.
The -35 box is located approximately 35 nucleotides upstream of the nucleotide transcription start site.
These are specific DNA sequences for the RNA polymerase to recognise and bind to so it knows where to start transcribing.
Promoter recognition initiates transcription.
What is sigma factor and what does it do?
It is a subunit of the RNA polymerase that recognises and binds to the promoter.
It is released to begin the elongation phase.
- Subunit
- Recognizes
- Binds
- Released
What does a rudder do?
Direct DNA and RNA strands on where they need to go
What is the coding strand?
The strand we don’t use to transcribe RNA. It is complementary to the template strand and is the non-template strand.
Therefore, the final transcription is nearly identical to the coding strand - it codes what the RNA will look like.
How does RNA polymerase know when the job is done?
It uses termination signals.
What is rho-dependent termination?
It occurs when the rho protein runs into the RNA polymerase to stop transcription after the RNA polymerase slows down.
What is rho?
A protein that follows behind polymerase on the growing mRNA chain.
What is rho-independent termination?
It is termination that depends on the formation of an mRNA hairpin that destabilizes polymerase.
Some RNA don’t have the sequence that can make the hairpin so they depend on rho.
This processes of independent of the rho protein and uses the hairpin to clog the whole through which transcription is happening to destabilizes polymerase and stop the process - it just drops off
Why the A-T region?
Evolution.
