Transcription Flashcards
Central Dogma
DNA—>RNA—->Protein
What is the specific relationship between genes and enzymes?
One gene-One polypeptide
What is responsible for coding of a polypeptide?
A gene
What 3 things depend on properties of proteins?
- Structure
- Function
- Development
Transcription
synthesis of an RNA copy of a segment of DNA;
DNA in nucleus, proteins synthesized in cytoplasm—-> needs a messenger—->RNA
Translation
Conversion of mRNA sequence into polypeptide
Structure of RNA
Contains uracil in place of thymine
has a hydroxyl group on the 2’ carbon atom of its sugar that makes it more reactive than DNA
What types of RNA are transcribed from DNA?
- mRNA
- rRNA
- tRNA
What are the steps needed to turn DNA into a protein?
- DNA
- Transcription
- mRNA, rRNA, tRNA
- Ribosomes
- Translation
- Protein
mRNA
encodes amino acid sequence of polypeptides
tRNA
brings amino acids to ribosomes during transcription
rRNA
functional and structural components of ribosomes
snRNA
small neclear RNA, role in RNA processing
Transcription Process
- Initiation: Promoter interacts with RNA polymerase to begin process
- Elongation: DNA is transcribed into RNA transcript
- Termination: transcription stops
Promoter
tells RNA Poly where to start copying
Coding sequence
Transcribed “RNA to be”
Terminator
Tells RNA Poly where to stop coding
Promoter
Sequences critical for specifying initiation of transcription
RNA polymerase binds to promoter
1st loosely to the -35 box while DNA is still double stranded
Binds more tightly and DNA unwinds at -10 box
Elongation
Transcription Bubble
RNA polymerase untwists DNA as it moves along strand
Temporary DNA-RNA hybrid formed at a rate of 30-50 nucleotides/sec
Termination sequence
Specifies where transcription will stop
Recognized by RNA polymerase or rho (protein)
RNA polymerase dissociates and it stops
What are the 3 polymerases of RNA?
RNA poly I: mostly rRNA synthesis
RNA poly II: mRNA and some snRNA
RNA poly III: tRNA and some snRNA
what is precursor mRNA?
product of transcription that has to be processed to produce functional mRNA
Precursor mRNA contains?
- Introns: intervening seq not translated
- Exons: expressed seq, translated
mRNA splicing
removal of introns from precursor mRNA
What two things are added to mRNA during RNA processing?
Modified at both 5’-3’ ends
5’ gets an additional G - 5’ capping
3’ gets an additional poly AAAA tail
