Chapter 12 - BSC 1010 Internet Dr. Presley Chapter 12 GENE...

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BSC 1010 – Internet Dr. Presley Chapter 12 GENE to PROTEIN GENE : (genetics) = unit of inheritance that affects a phenotypic character (biochemical) = a nucleotide sequence in DNA that directs the synthesis of a specific polypeptide NOW == a region of DNA whose final product is either a polypeptide or an RNA molecule Genes store information, control cell activity, and control development ONE GENE--ONE POLYPEPTIDE HYPOTHESIS - One gene -- one enzyme hypothesis 1940s Beadle and Tatum “The function of a gene is to control the production of a single, specific enzyme.” - used metabolic mutants of bread mold Neurospora crassa (an Ascomycota) - remember these are haploid cells, easy to follow inheritance - Study Figure 12.1, p. 235 this study using the nutritional mutants helped delineate the arginine synthesis pathway involving several enzymatic steps. today: - modified Beadle and Tatum statement since not all proteins function as enzymes and some proteins have more than one polypeptide chain “The function of a gene is to control the production of a single, specific polypeptide.” PROTEINS = polypeptide chain of amino acids arranged in a specific primary structure - the primary structure determines its higher conformation - functional types: enzymes, structural, hormones, transport, receptor, etc - are the links between genotype and phenotype: - it has been said that you are what you are because of your genes; actually you are what you are because of your proteins - next we study how genetic information encodes for specific proteins Central Dogma of molecular biology: Fig. 12.2, p. 236 Proposed by Francis Crick DNA RNA protein Transcription Translation Replication This process is not reversible in the cell. 1. DNA is copied in an exact manner from the original DNA of a cell. ( DNA replication ) 2. All types of RNA are manufactured at the template strand of DNA. ( transcription ) 3. Proteins are manufactured in the cytoplasm using the information passed from the gene to the RNA molecule. The sequence of amino acids in the protein is specified by the nucleotide sequence of the RNA. ( translation ) Study the Figure 12.3 on page 237 RNA virus modifies central dogma the RNA virus (called retrovirus) uses the enzyme reverse transcriptase to make DNA from RNA. This is a very useful tool in biotechnology. Transcription Transcription DNA RNA Protein Retrovirus Reverse Transcriptase Overview of PROTEIN SYNTHESIS : In Eukaryotic cells : 1. Transcription - DNA of nucleus directs the synthesis of messenger RNA, occurs in the nucleus, copies specific sequence of bases in the gene into the pre-mRNA molecule (or primary transcript of RNA) 2. RNA processing - enzymes at splicesomes remove non-coding sequences, - mature mRNA exits through the nuclear pores into the cytoplasm. - Study Figure 14.10 on page 289
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Chapter 12 - BSC 1010 Internet Dr. Presley Chapter 12 GENE...

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