Gene Expression and Protein Synthesis Overview

tRNA

converts the language of nucleic acids to amino acids

rRNA

is synthesized in the nucleolus and functions as an integral part of the ribosome machinery

mRNA

has the information specifying the amino acid sequence

Order of sequences on mRNA

5'UTR & shine-Dalgarno sequence → start codon → coding region → stop codon → 3'UTR

Peptide bonds

link individual amino acids together into a chain, made by peptidyl transferase

A site

aminoacyl-tRNA binds to A site

P site

holds the tRNA that carries the polypeptide chain

E site

uncharged tRNA unbinds the mRNA and exits

Genetic code

includes 64 codons, of which 61 specify 20 amino acids, making it degenerate (redundant)

Wobble position

synonymous codons often differ at the third nucleotide position

AUG

is the start codon, recognized as the start site through signals in the mRNA and ribosome binding context

Transcription in prokaryotes

is coupled because everything happens in one spot

Initial binding of mRNA in prokaryotes

shine-Dalgarno

Initial binding of mRNA in eukaryotes

7-methyl guanosine cap

Primary protein structure

linear amino acid sequence, chaperone proteins help with folding

Secondary protein structure

2 main structures, Alpha helix and beta sheets, made by hydrogen bonding between backbone elements

Tertiary protein structure

3D Structure determined by hydrophobic and ionic interactions as well as hydrogen bonds and Van der Waals interactions among side chains

Quaternary protein structure

Proteins made up of two or more polypeptides have a quaternary structure

Operon

Several genes controlled by a single promoter

Operon regions order

The promoter, the operator, the repressor

Lac Z

Cleaves lactose and lactose analogs to produce glucose and galactose.

Lac Y

Membrane protein required for transport of lactose and analogs into the cell.

Lac A

Covalently modifies lactose and analogs; acetylation of nonmetabolizable lactose analogs prevents their toxic buildup.

Repressor

Only bound in the absence of lactose.

Trp Operon

Synthesize of tryptophan.

Affecter molecule in the Trp Operon

Tryptophan itself.

Catabolism

Operons involved in catabolism are typically inducible; the substance to be broken down acts as the inducer.

Anabolism

Operons involved in anabolism are typically repressible; the inhibitor or corepressor is the small molecule that is the product of the operon.

Inhibit translation

Binding next to the Shine-Dalgarno sequence and/or the start codon blocks the ribosome from initiating translation.

Anti sense RNA

An RNA strand that is complementary to mRNA, bonds and prevents translation.

General transcription factor (GTF)

Required for RNA pol binding to core promoter or progression to the elongation stage.

Regulatory transcription factor (RTF)

Regulate the rate of transcription; some influence transcription initiation.

Activator

A regulatory protein that increases the rate of transcription.

Silencer

The sequence the repressor binds to.

Enhancer

The sequence the Activator binds to.

Repressor

A regulatory protein that decreases the rate of transcription.

Histone modifications

Acetylation turns gene on.

Combinatorial Control

A combination of many factors determines the expression of a given gene.

Steroid hormones end goal

The ultimate action of a steroid hormone is to affect gene transcription; the hormone binds to its receptor, and this complex then acts as a transcription factor.

ATP-dependent chromatin remodeling complexes

May change the positions of nucleosomes, evict histones, and/or replace histones with histone variants.