4.2 Protein Synthesis Flashcards
what is the first step in transcription?
The length of DNA that is going to be transcribed onto an RNA molecule is called the transcription unit. A transcription unit will be preceded by a sequence of bases- a promoter- called the TATA box (TATAAAA).
what is the second step in transcription?
A promoter initiates transcription, and the TATA box helps the enzyme figure out where to bind to the strand.
what is the third step in transcription?
RNA polymerase moves downstream (3’ -> 5’) from the TATA box, breaking down the hydrogen bonds between the nitrogenous bases
what is the fourth step in transcription?
Free RNA nucleotides are attracted to the exposed complimentary DNA bases.
a) C matches G and G matches C
b) U matches A and A matches T
what is the fifth step in transcription?
RNA polymerase joins the RNA nucleotides together, forming pre-mRNA
what is the sixth step in transcription?
The DNA behind the RNA polymerase re-joins into a double helix
what is the seventh step in transcription?
When the RNA polymerase reaches a “stop” codon/termination signal, the chain is terminated, and the pre-mRNA detaches
what is the eighth step in transcription?
A 5’ cap is added to the pre-MRNA, alongside the poly-A tail (250 adenines). These make it easier for the mRNA to leave the nucleus and help protect it from degradation from passing enzymes.
what is the ninth step in transcription?
Splicing of pre-mRNA occurs, forming mRNA. This mRNA moves out of the nucleus
what is the first step in translation?
mRNA attaches to the ribosome at the “start” codon – AUG
what is the second step in translation?
tRNA with a complementary anticodon attaches to the mRNA – UAC. This tRNA is attached to an amino acid – methionine
what is the third step in translation?
A secondary tRNA molecule, with the complimentary anticodon for the next codon onwards attaches to the mRNA
what is the fourth step in translation?
The ribosome moves along the mRNA bringing together 2 tRNA molecules at any one time.
what is the fifth step in translation?
The enzyme peptidyl transferase and ATP are used to join the amino acids with a peptide bond.
what is the sixth step in translation?
A third tRNA molecule attaches to the mRNA whilst the first tRNA is released and can collect another amino acid from the amino acid pool in the cell.
