Translation and Transcription in Eukaryotes Flashcards
What is Translation ?
Process of synthesis of proteins by encoding information on mRNA .Subsequent post translational processing of the protein molecule .
What is Transcription ?
Production of messenger RNA (mRNA) by the enzyme RNA polymerase and processing of the resulting mRNA molecules .
Where does the Eukaryotes Transcription occur ?Where does Prokaryotes occur ?
Occurs inside the nucleus .Later mRNA is transported to the cytoplasm for translation
Prokaryotes couples transcription and translation meaning they both occur stimulatory within the process of transcription going on translation has already started .
Difference between Prokaryotes and Eukaryotes ?
Prokaryotes transcription occurs in the cytoplasm alongside translation ./Coupled
Eukaryotes occur in the nucleus Later mRNA is transported to the cytoplasm for translation
Eukaryotes have three types of RNA polymerase whereas Prokaryotes have a single RNA polymerase .
5 cap and Poly tail
What is the initiation of Eukaryotes ?
first, the tRNA carrying methionine attaches to the small ribosomal subunit. Together, they bind to the 5’ end of the mRNA by recognizing the 5’ GTP cap (added during processing in the nucleus). Then, they “walk” along the mRNA in the 3’ direction, stopping when they reach the start codon (often, but not always, the first AUG).
What happens during the process of elongation ?
Our first, methionine-carrying tRNA starts out in the middle slot of the ribosome, called the P site. Next to it, a fresh codon is exposed in another slot, called the A site. The A site will be the “landing site” for the next tRNA, one whose anticodon is a perfect (complementary) match for the exposed codon.
Once the matching tRNA has landed in the A site, it’s time for the action: that is, the formation of the peptide bond that connects one amino acid to another. This step transfers the methionine from the first tRNA onto the amino acid of the second tRNA in the A site.
! The methionine forms the N-terminus of the polypeptide, and the other amino acid is the C-terminus.
Formyl Methione
What happens during the process of Termination ?
Stop codons are recognized by proteins called release factors, which fit neatly into the P site (though they aren’t tRNAs).
Release factors mess with the enzyme that normally forms peptide bonds: they make it add a water molecule to the last amino acid of the chain. This reaction separates the chain from the tRNA, and the newly made protein is released.
What about the 5 cap ?
The 5’ cap is added to the first nucleotide in the transcript during transcription. The cap is a modified guanine (G) nucleotide, and it protects the transcript from being broken down.
It also helps the ribosome attach to the mRNA and start reading it to make a protein.
What about RNA splicing what happens to the introns ?
In RNA splicing, specific parts of the pre-mRNA, called introns are recognized and removed by a protein-and-RNA complex called the spliceosome. Introns can be viewed as “junk” sequences that must be cut out so the “good parts version” of the RNA molecule can be assembled.
What happens to the exons?
The pieces of the RNA that are not chopped out are called exons. The exons are pasted together by the spliceosome to make the final, mature mRNA that is shipped out of the nucleus.
only the exons of a gene that encode a protein. Not only do the introns not carry information to build a protein, they actually have to be removed in order for the mRNA to encode a protein with the right sequence. If the spliceosome fails to remove an intron, an mRNA with extra “junk” in it will be made, and a wrong protein will get produced during translation.
