In Class Notes 2/27

Amino Acids - 20

Reading a Codon Chart

• A codon chart shows us how to convert 3 nucleotides (UCAG) into an amino acid

• Codon- A three-base sequence of RNA

• “Encodes” for an amino acid

• mRNA is read in terms of codons

• UUU => phe (phenylalanine) STOP

• AUG => Met (methionine) START

Ribosomes “translate” mRNA to assemble amino acids

• With the help of tRNA, ribosomes add amino acids in a polypeptide chain

• tRNA transfer RNA

Anticodon: the matching 3 base sequences on the tRNA

start - end

CGAUG|ACC|UGG|AAC|UAAUCG

Genetic Mutations can affect the shape of proteins

• Sickle shape - lose surface area and therefore the amount of oxygen that the red blood cell can hold, and they are more prone to clotting

Sickle cell disease is caused by a change to nucleotide sequence

• Hemoglobin - the protein that binds oxygen in red blood cells

• Normal hemoglobin DNA sequence:
  DNA ⇒ ...TGA GGA CTC CTC...
  mRNA ⇒ ...ACU CCU GAG GAG...
  Amino acids ⇒ ...Thr - Pro - Glu - Glu...
  Mutated hemoglobin DNA sequence:
  DNA ⇒ ...TGA GGA CAC CTC...
  mRNA ⇒ ...ACU CCU GUG GAG...
  Amino acids ⇒ ...Thr - Pro - Val - Glu..

• Super charged → no charge

Clinical applications of the central dogma

Membrane Transport and Cell Signaling

Transport across the Cell Membrane

• Selective permeability