One Gene – One Polypeptide SBI 4UI – 5.1

Gregor Mendel Grew pea plants Certain “factors” responsible for patterns of inheritance Today: “factors” known as genes Genes direct the production of proteins Proteins determine phenotype and drive cellular processes

Garrod’s Hypothesis British physician Certain illnesses recur in some families Determined that certain chemicals were present in people with a specific disease Hypothesized that enzymes are under hereditary control Error in hereditary material = enzyme error

Guess Who?

Beadle & Tatum Experimented with red bread mould Healthy Neurospora crassa can synthesize all the complex amino acids and vitamins Defective strains cannot Mutations caused changes in specific enzymes involved in metabolic pathways

One Gene – One Enzyme Concluded that a gene acts by directing the production of only one enzyme They proposed the one gene – one enzyme hypothesis

Vernon Ingram Studied hemoglobin protein in people with sickle cell anemia Substitution of a single amino acid led to a change in the structure of hemoglobin He linked hereditary abnormality to a single amino acid alteration

One Gene – One Polypeptide We know that genes code for enzymes and proteins

To Do Section 5.1 Understanding Concepts #1-3