Amino acids

Knockout mouse: genetically engineered mouse in which researchers have inactivated an existing gene (by replacing it/disrupting it w/ artificial DNA) to produce a change in phenotype. 

To study functions of genes that have been sequenced.

• 1. Target specific gene to eliminate exons and put in a Neo gene for selection
• 2. Gene lacks certain exons and codes for defective protein.
• 3. Selet the embryonic stem cells containing targeted defective gene by growing antibiotic (cells that express Neo (neomycin) will grow. Cells w/o it will die). 
• 4. Inject ES cell into blastocyst
• 5. Implant blastocyst into pseudo-pregnant mouse. 

Maternal antibodies in breast milk

1. HCl denatures proteins for subsequent hydrolysis by proteases

2. Pepsinogen is secreted from chief cells and is activated to pepsin by HCl or autocatalytically by other (activated) pepsin molecules.

Pancreas produces pancreatic proteases that cleave large polypeptides from stomach into oligopeptides/amino acids. 

Each protease has a different specificity for the R group adjacent to the peptide bond.