Final exam review - Start codon- AUG. Stop codon- UGA, UAA,...

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Start codon- AUG. Stop codon- UGA, UAA, UAG Transcription is the synthesis of an mRNA version of the instructions stored in DNA Prokaryotic RNA polymerase is a holoenzyme – an enzyme made up of a core enzyme and other required proteins. The core enzyme has the ability to synthesize RNA. Transcription of bacterial genes is initiated at specific sections of DNA called promoters . Sigma opens the DNA double helix. The template strand is threaded through the RNA polymerase active site. An incoming ribonucleoside triphosphate (NTP) pairs with a complementary base on the DNA template strand, and RNA polymerization begins. Sigma dissociates from the core enzyme once the initiation phase of transcription is completed. Pro. Vs Eu. Transcription Eu. Trans. Is initiated by basal trans. Factors. Eu. Cells contain 3 types of RNA polymerase. Eu. Promoters are more diverse/complex. Many promoters recognized by RNA polymerase 3 include a seq. called TATA box. A primary RNA transcript contains exons and introns. Exons are the coding regions that will be part of the final mRNA product. Intervening noncoding sequences are called introns. Introns are removed by splicing. sNRPS (small nuclear ribonucleoproteins) form a complex called a spliceosome. Catalyzes the splicing reaction. Primary RNA transcripts are also processed by the addition of a 5’ cap and a poly (A) tail. The cap serves as a recognition signal for the translation machinery. The Poly (A) tail extends the life of an mRNA by protecting it from degradation. In translation , the sequence of bases in the mRNA is converted to an amino acid sequence in a protein. Ribosomes catalyze translation of the mRNA sequence into protein. In bacteria, transcription and translation can occur simultaneously (No nucleus separating). In eukaryotes, transcription and translation are separated (mRNAs need to be shipped out of the nucleus). In prokaryotes, multiple polymerases/ribosomes can be active at once. One RNA can support multiple ribosomes – polyribosomes. tRNA s- The adapter molecule was later found to be a small RNA called transfer RNA (tRNA) A tRNA covalently linked to its corresponding amino acid is called an aminoacyl tRNA . Enzymes called aminoacyl tRNA synthetases catalyze the addition of amino acids to tRNAs . Roles of tRNAS - There is a different aminoacyl tRNA synthetase and one or more tRNAs for each amino acid (20). Each tRNA carries a specific amino acid that can be transferred to a protein. RNA codon interacts with correct tRNA to bring in correct amino acid. Ribosomes - Ribosomes contain both protein and ribosomal RNA (rRNA) . The ribosome is considered a ribozyme , Active sites almost entirely RNA, Protein is imparting stability and structural support. From chapter 7, the nucleolus is the spot in the nucleus where rRNA is synthesized. Ribosomes can be separated into two subunits. During translation, tRNAs are found at three sites in ribosomes. Translation action - An aminoacyl tRNA carrying the correct anticodon for the mRNA codon enters the A site. A peptide bond forms between the amino acid on the aminoacyl tRNA in the A site and the growing
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This note was uploaded on 11/17/2010 for the course BIO 311 C taught by Professor Mcclelland during the Spring '09 term at University of Texas at Austin.

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Final exam review - Start codon- AUG. Stop codon- UGA, UAA,...

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