BIOL 300 Summer 4.3 Study Guide

Protein encoding/structural genes

Genes that encode amino acid sequences of polypeptides

mRNA

Product of transcription

Translation

Process of converting mRNA into amino acids

Codons

Three nucleotide base sequences

Sense Codons

Codons that specify an amino acid

Example of a Sense Codon

UAC = Tyrosine

Start Codon

AUG, which signals start of translation by methionine

Stop Codons

UAG, UAA, UGA which signals the end of translation

Degeneracy

The concept that states that multiple codons can code for the same amino acid.

Synonymous Codons

The actual codons that can specify for the same amino acid

Why do we need 3 bases for a reading frame?

We need a reading frame of 3 bases because we need enough bases to code enough for a total of 20 amino acids

Reading Frame

Group of 3 bases determined by AUG; shifting frame changes amino acid sequence

Anti-Codon

3-base sequence on tRNA that binds mRNA codon

Acceptor stem

Part of tRNA where an amino acid attaches; contains CCA at 3' end

Charged tRNA

tRNA with an amino acid attached to it

Aminoacyl-tRNA synthetase (Study the Mechanism)

Enzyme that catalyze attachments of

amino acid to tRNA molecule =

essential for tRNAs to function

Error rate of synthetase

Less than 1 in 10,000 tRNAs get the wrong amino acid.

Codon Variation Site

Usually occurs at the 3rd position of the codon

Wobble Effect

3rd Codon base allows mismatches; enables fewer tRNAs to recognize multiple codons.

Mechanism for Aminoacyl-tRNA Synthetase

1. Synthetase binds AA and ATP

2. Hydrolyze ATP, AMP attaches to AA. Phosphate released.

3. Correct tRNA binds to synthetase > AA Covalently attaches to 3' CCA in acceptor > AMP released

4. Final step is tRNA w/AA released from enzyme now charged

Isoacceptor tRNAs

tRNAs with different anticodons that carry the same amino acid

Can tRNA recognize multiple codons?

Yes, due to the wobble effect

Site of Translation

Ribosome

# Ribosome Types

1 in bacteria, multiple types in eukaryotes

Ribosome Subunits

Prokaryotic (50S/30S)

Eukaryotic (60S/40S)

What are S units

Svedburg Units

Polysome and its benefits?

Multiple ribosomes translating one mRNA, this is beneficial because it allows for efficient quick translation

Where does mRNA sit on the ribosome?

Surface of Small Subunit

What are the three important binding sites on a Ribosome?

A, P, and E

What is the initiator tRNA in bacteria.

Carries the f-met amino acid

Shine-Dalgarno Sequence

Ribosomal binding site in prokaryotes that helps the ribosome find the start codon

What does the 5' G cap do?

Helpes ribosome bind mRNA in Eukaryotes

What does 16S rRNA do?

Decoding function, detects tRNA bound to A site if it is matched correctly

Termination

Release Factor 1 or 2 will bind to a STOP codon and then RF3 binds to a different site of ribosome which will now bond between polypeptide and tRNA is hydrolyzed and released from ribosome.