Protein Synthesis

What is genetic code?

Sequence of base pairs

What are introns

A non-coding region

What are exons?

A coding region

What is a start codon?

AUG (Methionine)

What is a stop codon?

UAA, UAG, UGA

What are the 4 main steps?

Transcription, Post- transcription, translation, Termination

Where does transcription occur?

In the nucleus

Describe transcription.

1. Initiation: unwind/unwrap the section of the chromosome that contains the gene. RNA polymerase attaches to a promoter sequence.
2. Elongation: RNA polymerase builds the mRNA molecule while using DNA as a template.
3. Termination: RNA polymerase reaches a termination sequence.

What is a promoter sequence?

An area in the code rich in T and A

Describe post transcriptional?

Introns are cut out and exons are put together. 5’ cap is added to mRNA so ribosomes can bind. Poly-A tail onto 3’ end to stabilize.

Describe Translation

1. Assembly: SRS attaches to 5’ cap of mRNA. SRS travels down until a start codon is found. tRNA with MET binds to mRNA. LRS attaches onto complex with 1st tRNA in p-site. The next codon is exposed in a-site.
2. Elongation: next tRNA carries a.an into a-site. Peptide linkages form between a.a in a-site and p-site. A.a in p-site is released from tRNA. tRNA in p-site leaves and the one from a-site with the a.a chain shifts to replace it. Repeat.

Describe termination

When a stop codon enters the a-site, no tRNA enters. Release factors will enter and the a.a chain releases