From Gene to Polypeptide, Codons, & Exons/Introns

Archibald Garrod

studied the inherited disease alkaptonuria

what was A. Garrod’s hypothesis

“one gene, one enzyme”

alkaptonuria (dark urine disease)

phenylalanine (amino acid that breaks N) → homogentisic acid: when oxidized (not flushed) it turns black

what did G. Beadle & E. Tatum modify Garrod’s hypothesis into

the “one gene, one protein (polypeptide)” hypothesis

why did Beadle & Tatum modify Garrod’s hypothesis

because all enzymes are proteins, but not all proteins are enzymes

what are the 2 steps that genetic code converts into a polypeptide

transcription & translation

codons

basic unit involved in translation consisting of triplets of nucleotides

what is the # of possible codons

4³ = 64

what are also added into the total codon count

stop codons & start codons

exons

translatable regions

introns

non translatable region