Molecular Genetics Flashcards
Repression:
Stops expression of tryptophan operon
Attenuation:
Can stop expression of Tryptophan operon by causing transcription to fail
Steps of Transcription:
1) DNA is unwound by RNA polymerase
2) RNA polymerase runs along template strand 3’ - 5’ making mRNA
3) mRNA separates from template strand and DNA joins back up
Where does Transcription occur?
Nucleus (Eukaryotes); Cytoplasm (Prokaryotes)
Steps of RNA processing:
1) Introns spliced out of pre-mRNA
2) Exons ligated back together
3) Methyl cap added to 5’ end of mRNA (protect against enzyme attack)
4) Poly-A-Tail added to 3’ end of mRNA (protect against enzyme attack)
Where does RNA processing occur?
Nucleus (Eukaryotes); not at all (Prokaryotes)
Steps of Translation:
1) 5’ end of mRNA enters ribosome
2) tRNA molecules which have an amino acid on one end and anticodon on other air with complementary codon
3) Peptide bonds form between amino acids to form a polypeptide
Where does Translation occur?
Ribosomes
Where is the Stop codon located?
At the 3’ end of the transcribed mRNA sequence
Where is the Start Codon located?
At the 5’ end of the transcribed mRNA sequence
Role of mRNA
Contains the code for the synthesis of the protein
Role of tRNA
Transfers amino acids to the ribosomes
Role of rRNA
- Helps peptide bond formation
- Helps mRNA and tRNA interactions
- Forms structure of ribosome
Structural Genes…
… Code for proteins that serve as cellular structures and enzymes
