Lecture 17 - Gene expression II (translation and point mutations)

If you add a radioactive amino acid to an in vitro protein synthesis system (mRNA, tRNA, ATP, required enzymes and proteins, amino acids, ribosomes in a test tube), where will

you find the radioactive amino acid?

Attached onto a tRNA → transiently associated with ribosome → incorporated into a protein

What hypotheses are there for how codons interact with amino acids?

Hypothesis 1: Amino acids interact directly with mRNA codons

Hypothesis 2: Adapter molecules hold amino acids and interact with mRNA codons

How does an aminoacyl tRNA read a codon?

Crick proposed the wobble hypothesis

There are ___ different codons but only about ___ tRNAs in most cells

61; 40

What can the anticodon's third position form?

A nonstandard base pair

What is one tRNA able to base-pair with?

More than one type of codon

Where are ribosomes found in eukaryotes?

1. Free ribosomes - cytosol

2. Bound ribosomes - attached to RER

3. organelle ribosomes - mitochondria , chloroplast

Where are ribosomes found in bacteria?

ribosomes - cytosol. In bacteria, transcription and translation are simultaneous (coupled