Chapter 12Gene Expression and Regulation Part 1 of 2How does your genotype become your phenotype? 1. DNA is transcribed into RNA 2. RNA is translated into protein DNA provides instructions for protein synthesis. The message is carried by ____________________ (ribonucleic acid) -DNA is in the nucleus (for eukaryotes) Protein synthesis occurs in the cytoplasm -So DNA cannot directly guide protein synthesis The message must be carried from the DNA in the nucleus to the ribosomes in the cytoplasm RNA (ribonucleic acid) RNA differs structurally from DNA: Usually ________________________________________ RNA contains the sugar ribose instead of? RNA uses the base Uracil (U) instead of Thymine (T) Three types of RNA aid in protein synthesis 1. __________________ RNA (mRNA) 2. _________________ RNA (rRNA) 3. ________________ RNA (tRNA) Comparing nucleic acids: DNA and RNA Table 12.1 Major types of RNA (ribonucleic acid): mRNA ( messenger ) Fig. 12.1 Carries the code for protein synthesis from DNA to ribosomes Groups of three bases called ____________________ specify which amino acid will be added to a polypeptide chain during ____________________
Major types of RNA (ribonucleic acid): rRNA ( ribosomal ) -rRNA and proteins form ribosomes. -Ribosomes are the site of protein synthesis during translation -Made of one large and one small ____________________ Fig. 12.1 Major types of RNA (ribonucleic acid): tRNA ( transfer ) Carries amino acids to the ribosomes for protein synthesis during translation. tRNA are specific for each amino acid : ____________________________________________________________ directing the correct amino acid to be attached to the growing polypeptide chain. Fig. 12.1 • Genetic information is transcribed into RNA and translated into protein. Fig. 12.2 DNA is transcribed into RNA RNA is translated into protein Transcription (from nucleotide sequence to nucleotide sequence) DNA => RNA A gene is a segment of DNA that can be copied into RNA. Occurs in the nucleus Translation (from nucleotide sequence to amino acid sequence) ____________________ Occurs in the ____________________ • Transcription: DNA RNA Occurs in the nucleus Transcription consists of three steps 1. Initiation 2. Elongation 3. Termination Corresponds to three spots on most genes A promoter region The “ body ” of the gene A termination signal • Transcription : initiation Initiation begins when RNA polymerase binds to the promoter region of a gene. RNA polymerase – enzyme that synthesizes RNA Promoters (in eukaryotes) consist of two main parts
- The area that RNA polymerase binds -TATAA box -One or more other regions called transcription factor binding sites • Transcription: initiation. Fig. 12.3 • Transcription : elongation Elongation- generates a growing strand of RNA RNA polymerase travels down the template strand of DNA synthesizing RNA with complementary bases to the template strand RNA polymerase reads DNA 3’=>5’ RNA polymerase synthesizes RNA 5’=>3’ DNA – TACCCTCAA RNA – AUGGGAGUU • Transcription: elongation. Fig. 12. 3
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