GO!3 (Translation)

Codons

three nucleotide sequences in RNA that are read to code for a specific protein

Reading frame

the way the codons are read, heavily critical to the proteins created, so the reading frame set has lots of impact.

How many reading grams can we have

3, shift let, shift right and the middle

tRNA

translator RNA that reads codons and brings the correct amino acid there (read & bring in)

tRNA’s structure (important bits)

1. Folded RNA

2. Anticodon loop

3. Attached amino acid at the 3’ end covalently

4. Clover shape

Functional RNA

RNA that is not translated into a protein

Anticodon

part of the tRNA that comp base pairs with the specific codon within the mRNA while inside the Ribosome

Amino Acid on tRNA

added to the 3’ end covalently and is the amino acid of the codon in the RNA sequence

Aminoacyl- RNA synthetase

specific enzyme for each tRNA that adds the amino acid to the 3’ end of the tRNA

Aminoacyl- RNA synthetase function

1. Ensures that the anti-codon is correct by making sure that the anticodon matches the amino-acid added and if not checked it adds the wrong amino acid.

2. leaves a high energy bond that drives polypeptide chain formation

TOP hat Question: The anti-codon is 5’ UAA’ 3 what is the codon

5’ UAA 3’

Relationship between anti-codon and codon

the anti-codon and codon complementary base pair attaching the tRNA to the specific segment RNA is corresponds to.

Genetic Code is Degenerate

multiple codons encode for the same amino acid

How is genetic code degenerate

1. A single tRNA recognizing more than one codon due to expanded base paring WOBBLE

2. more than one tRNA for an amino acid

Wobble

tRNA with nearly perfect anti-codons but the third nucleotide is incorrect, creating a wobbly, short-lived bond that still does the job.

Ribosome Definition and function

huge protein and RNA complex that decodes the the RNA with its EPA pockets

RIbosome anatomy

a ribosome with a large and small subunit that form the 3 pockets EPA

EPA

exit site, peptide site(pass), and aminoacyl site (add) , which are pockets formed inside the ribosome when the large and small subunit come together.

E site (exit site)

the site where the tRNA is ejected

Peptidyl site (pass site)

where the bond between the amino acid and tRNA are broken and the amino acid is bonded to the amino acid in the aminoacyl site

Amioacyl site (add)

where new tRNA holding another amino acid situates itself for bonding with the amino acid in the p site

C terminus

the side in which proteins are added

N terminus

the side that comes out of the ribosome first and never has addition to that side

Hey! go back to the slides and walk through the different steps of translation !

fine

Eukaryotic Translation Initiation

1. small ribosomal subunit binds with the tRNA and finds the 5’ cap

2. After finding the cap it scans 5’ to 3’ for the AUG methionine sequence

3. Initiation factors disassociate and th large ribosomal subunit binds, putting methionine in the p-site

4. another tRNA comes through and goes to the A site

5. Peptide bond is formed, and EPA stepwise happens

Purpose fo methionine (AUG)

it is always the start codon and let;s the ribosome and tRNA know where to start

Prokaryotic Translation Initiation

Shine- Dalgarno sequence complementary base pairs with the ribosomal RNA (small subunit) and positions the P site over an AUG (meth).

Ribosomal RNA

small subunit of the RNA

Release factor

protein that recognizes stop sequences and catalyzes a hydrolysis reaction, breaking the bond between the tRNA and the growing polypeptide chain causing ribosome to disassociate. (looks like and fits into the p site)

Read Through Mutation

when the stop codon is mutated into a regular codon in turn not having the Ribosome stop, reading throguh and creating longer and wrong protein.

Polycistronic mRNA

meaning that one mRNA can make multiple polypeptide chains/proteins and only occurs in bacteria!!!

Are polycisitronic proteins related to each other?

NO! they can be vastly different!

why do bacteria have polycistronic mRNA

they can have multiple shine-dalgarno sequences followed by AUG(meth) sequences anywhere inside the sequence

Monocistronic mRNA

one gene, one mRNA, creating ONE proteins and this occurs in eukaryotic cells

Why do eukaryotes have only monocistronic mRNA

because the tRNA and ribosome can only bond at the 5’ cap and there aren’t multiple 5’ caps within mRNA.

Polysome

many ribosomes binding to a single mRNA and creating lots of protein from one mRNA

Always read RNA

5’ to 3’ since that’s how Ribosome does it