The Flow of Genetic Information Flashcards
Three ways that genetic information flows
- Expression (DNA to Proteins)
- Recombination (DNA shared with other cells)
- Replication (DNA given to new generation of cells)
rRNA
Ribosomal RNA
- 5S, 16S, 23S
- Catalytic role
- 70% of cellular RNA
mRNA
Messenger RNA
- Informational role
- 10% of cellular RNA
tRNA
Transfer RNA
- Functional role
- 20% of cellular RNA
RNA Polymerase structure
- (in E.coli) has 5 subunits: α, β, β’, ω and σ
- α, β, and β’ synthesize RNA
- ω helps with enzyme assembly
- σ factor recognizes promotor region to initiate transcription (adds specificity)
- catalyzes phosphodiester bond formation between ribonucleotides
- DNA dependent, no primers needed
Protein Encoding Sequence Structure (DNA)
Promoter - RNA-coding sequence - Terminator
Protein Encoding Sequence Structure (mRNA)
Leader - Protein-coding sequence - Trailer
Promoter Structure
-35 sequence - variable sequence - Pribnow box (-10) - +1 (start transcription)
Terminator Structure
Contains A-U pairs with weak bonding
Initiation
RNA Polymerase binds to promoter sequence assisted by σ factor
Elongation
RNA Polymerase moves along template strand (antisense), opening a transcription bubble and ribonucleotides are added to 3’ -OH of preceding nucleotide
Termination
RNA Polymerase reaches a terminator sequence:
- Self determining/intrinsic/Rho independent: stem loop forms from transcribed RNA, pulling polymerase apart
- Enzyme/Rho dependent: terminator protein binds to terminator sequence on mRNA and yanks mRNA through it to push polymerase off
Why use operons?
Allows for related genes to be expressed and regulated together
Polycistronic mRNA arises from…
…transcription of operon genes that are on a single mRNA
AUG codes for…
N-formylmethionine
