Translation

What is the definition of Translation?

The process by which the genetic information encoded in mRNA is used to synthesize polypeptides (proteins).

Or the decoding of an mRNA message into a polypeptide chain

What is the importance of Translation?

Translation is essential for the expression of genes and the production of functional proteins necessary for cellular processes.

What is the readout of mRNA?

Translation

__codes for certain ___

mRNA codes for certain amino acids

What are polypeptides (proteins)?

String of amino a cids

Who allows for translation?

tRNA, it transfers the necessary information for protein to be made

Where does translation take place?

translation takes places on the ribosomes in the cytoplasm.

mRNA

the messenger RNA carrier the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm

Ribosomes

these are responsive for protein synthesis; they are composed of rRNA and protein.

Describe tRNA. Shape?

transfer RNA are molecules that bring amino acids to the ribosomes based on the codons on mRNA. + like shape

What is the building block of proteins, encoded by specific codons in mRNA and brought by tRNAs?

Amino acids

What officially begins the translation process?

When the mRNA attaches to a ribosome in the cytoplasm

what is rRNA, what does it do?, shape?

Ribosomal RNA combines with proteins to make ribosomes. Globular shape

What direction is the mRNA molecule being read during the translation process?

Read from 5’ to 3’.

What is an anticodon? What is it complementary to?

• 3 unpaired bases

• Complementary to 1 mRNA codon.

• The anticodon is the place where things are read.

• Anticodons are single stranded

How many kinds of amino acids are carried by tRNA? What determines this?

• The tRNA only carries a single kind of amino acid.

• What that amino acid is depends on what the anti-codon determines it to be.

Ribosome composition and function in protein synthesis.

• rRNA + protein = ribosome

• Function in protein synthesis: Ribosomes are the place where amino acids are assembled to produce proteins.

What is the significance of an anticodon?

Makes sure the correct amino acids are being incorporate into the polypeptide chain through complementary pairing with codons on mRNA>

What are the 3 steps of translation?

Initiation, Elongation, Termination

Describe step 1 of translation

Initiation

• At the 5’ cap, ribosomes assemble around the tRNA and “attach to the mRNA, scan for the start codon AUG, once it finds it binds to it, and then the large ribosomal subunit joins to form initiation complex, translation begins!

What is the start codon?

AUG

where to amino acids connect on the tRNA?

amino acids connect at the 3’ end of the tRNA.

The initiation (codon) will always always always ALWAYS start at what site?

It will start at the p-site.

Describe step 2 of the translation process

Elongation

• The polypeptide chain gets longer

• Translocation happens: Translocation → How the polypeptide chain shift within E,P, & A sites. Starts at P-site, then things are added to the A-site and shift the entire chain to the E site, then more and more things are added to the A-site, and more shifting happens, and boom a polypeptide chain.

• Translocation just keeps on happening until the end of the mRNA message is reached.

  • Bit more specific CODON RECOGNITION: The tRNA carrying the complementary anticodon binds to the mRNA codon in the A site of the ribosome.

  • Bit more specific PEPTIDE BONDS FORMATION: The amino acid in the P site forms a peptide bond with the amino acid in the A site, catalyzed by peptidyl transferase.

  • Bit more specific TRANSLOCATION: Ribosome moves along the mRNA, shifting the tRNA and mRNA by one codon, and the empty tRNA exist the ribosome from the E site. new tRNA enters at the A site.

Describe step 3 of the translation process

Termination

• As the mRNA keeps on being read, a stop codon is recognized by release factors. Once the release factor is recognized, translation simply stops by having a release factor bind to the A site and making the ribosome to release the completed polypeptide chain. The ribosome dissociates and the new protein is released.

What are the stop codons? Their release factors?

• UAA → U Ara Annoying (RF - 1 & RF -2)

• UGA → U Go Away (RF - 2)

• UAG → U Are Gone (RF -1)

Why is the genetic code represented by a three-letter code instead of a two-letter or one-letter code?

There are four different letters in total that can be coded. If 1 letter codes were coded, then 4¹ = 4, only codes for 4 amino acids, which is not enough for the total 20 amino acids that need to be coded for. If we have 4² = 16, only codes for 4 amino acids, not 20. but if we have 4³ = 64, this makes it possible to make 64 variations of amino acids, which is enough to cover the 20 that need to be coded for. This means there will be some redundancy, some amino acids will code for the same things, but that is okay.

How many sites does ribosome have for tRNA binding? What are they?

• 3 sies for tRNA binding

• E site: Exit Site

• P site: Peptidyl Site

• A site: Aminoacyl Site

What is used to decode DNA? What is this term? What does this term do?

The genetic code → concert mRNA 3 letter grouping called codons. Informs us what amino acid each codon codes for.

What does it mean when it is said that the genetic code is redundant?

For a genetic code to be redundant it refers to the fact that multiple codons can specify the same amino acids.

How was the genetic code found?

Synthetic DNA strands were made → the strands were stuck into bacteria → and then biologists looked at what proteins/ amino acids were made and found.

Is the genetic code universal?

The genetic code is universal.

Wobble Hypothesis

The Wobble Hypothesis states that it can inferred that the last letter of a code does not hold great importance. Ribosomes are “okay” with the last letter of a code not fitting in perfectly into the code, and therefore, continue with the translating process.

A code can be modified to alter it more towards another subject, make it more efficient, or make another species the desired proteins other than the one originally set.

Different species have different preferences towards codes, but these codes can be modified/altered/changed.

RNA starts at the what side? & ribosome forms. Where does everything else start at?

RNA starts at the p-Side

Everything else starts at the a-side

What does redundant mean?

When there are many ways to make triple groups (many ways to code for amino acids)