concept 17.1: genes specify proteins via transcription and translation

archibald garrod

first person to suggest that genes dictate phenoypes through enzymes that catalyze specific chemical reactions

describe the work that Archibald Garrod did

he thought the symptoms of an inherited disease reflected an inability to synthesize a certain enzyme and reasoned that the condition (alkaptonuria- condition where urine turns black then exposed to oxygen) is caused by inability to produce an enzyme that metabolized alkapton

George Beadle and Edward Tatum

hypothesized that the function of a gene is to dictate production of a specific enzyme- one gene, one enzyme hypothesis

describe the work that george beadle and edward tatum did

exposed mold to x-rays, creating mutants that were unable to survive on minimal media (minimal medium consists of inorganic salts and lacks amino acids) since they became unable to synthesize certain molecules. using crosses they identified three classes of arginine- deficient mutants, each lacking a different enzyme necessary for synthesizing arginine

what was the hypothesis revised to and why was it revised

one gene- one protein, not all enzymes are proteins

central dogma of biology

RNA is the bridge between genes and protein synthesis

what is transcription

the synthesis of RNA using information in DNA and production of mRNA

translation

the synthesis of a polypeptide using information in the mRNA

where does translation occur

ribosomes

in prokaryotes, does translation need to wait for transcription to finish

translation of mRNA can begin before transcription has finished

does mRNAs need to be processed in prokaryotes

they can be immediately translated without processing

where does transcription occur in bacteria cell

cytoplasm

where does translation occur in bacteria cell

cytoplasm

where does transcription occur in eukaryotic cell

in the nucleus

where does translation occur in eukaryotic cell

cytoplasm

what separates the transcription and translation in eukarytoic cells

the nucelar envelope

pre- RNA strand

the initial unaltered strand of DNA

in eukaryotic cells are mRNA altered before they go to be translated

they are modified before leaving the nucleus