Notes 11-25-09

Page 190

The connection between Genes and Proteins-The study of metabolic defects provided evidence that genes specify proteins-Genes => tell cells how to build proteins-Beadle and Tatum Experiment-One gene – One polypeptide

Beadle and Tatum Experiment

(Metabolic pathways

-Worked with fungus pathways-Final phase [d], grows from a.

-As long as DNA sequences are correct, all enzymes do the right thing.

-However, if gene is mutated and enzyme one does not work-A enzyme damaged, B can still transform into C and then D and work properly-A, B, C damaged, no-go, D directly would still work.-One gene affects particular enzyme, as gene makes enzyme.-One gene, one enzyme hypothesis-“One gene, one polypeptide/protein”.

-Gene simply instructs how to build protein

Bacterial Protein Synthesis-Make small copy of segment of DNA describing how to make small segment of protein-mRNA – messenger RNA – copy of gene-RNA – uracil instead of thymine-Complimentary base pairing system used. mRNA is like 2nd DNA strand.-Translate DNA/RNA to protein sequence

Eukaryotic Protein Synthesis-Transcription-RNA processing-Translation

-link up outside nuclear pore with ribsomes, ribosomes read code-in the genetic code nucleotide triplets, RNA [codons] speicy amino

acid sequence-codons tell which amino acid to place next in the polypeptide chain.-UUU = phenylalanine -UAA = leucine

-page 192 – genetic code chart

-AUG – Start codon – Methianine-STOP codons – UAA, UGA, UAG-First and last letter important, third not so much.-“Synonyms”

Transcription – Initiation-RNA polymerase-nucleotides can only be added to the three prime end of the RNA chain,

just like DNA-Sides pulled apart, temp strand read.-3 prime end toward 5 prime end read

Transcription – Elongation-Complimentary base pairing, attaching to 3 prime end-Adenine -> uracil-Cytosine -> guanine-Thymine -> adenine-Guanine -> cytosine

Transcription – Termination-Stop codon

Eukaryotic cells modify RNA after transcription-Introns => unusable information that needs to be cut out

-reattaches important part of RNA

-spliceosomes => part enzyme, part RNA perform this job.