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Biology Exam1 chapter 13

Biology Exam1 chapter 13 - Lecture#14 Chapter 13 Chapter 13...

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Lecture #14: Chapter 13 Chapter 13: Gene Expression and RNA and Protein Synthesis Sequence of bases -> code to specify amino acids in proteins Eukaryotes: DNA only in nucleus o Protein synthesis in cytoplasm o HOW?! RNA! -> in nucleus AND cytoplasm Bridges gap between nucleus and cytoplasm in prokaryotes and eukaryotes DNA to Protein o 1. Transcription RNA synthesis Sequence of bases in RNA becomes code to make the sequence of amino acids in the protein being made o RNA: ribonucleic acid Usually single stranded Sometimes internal complementary base pairing -> folds back on itself to make it sort of double stranded Uracil is substituted for thymine (U-A) Sugar is ribose (has extra O to make OH group) instead of deoxyribose (no O for OH group; just H) o RNA structure: SEE DIAGRAM o Transcription: synthesis of RNA DNA dependent RNA polymerase : enzyme that makes RNA copy that is complementary to one of the 2 DNA strands -> template (transcribed) strand Growing RNA Template DNA strand 5’ 3’ | U-------H--------- A | | G-------H--------- C | | A-------H--------- T | v v 3’ 5’ Anti-parallel Nucleotide added to growing chain by RNA polymerase Has same limitations as DNA polymerase o Can only add to growing 3’ end -> not too much of a problem because only one strand being synthesized Anti-parallel synthesis o The different strands can both be used as templates in different parts of the chromosome DIAGRAM IN NOTES o Promoter region: this is where you start transcription signal RNA o RNA probably came first -> before DNA -> RNA world! o mRNA: messenger RNA o rRNA: ribosomal RNA -> forms part of structure of ribosome -> structure and catalyst enzyme
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o tRNA: transfer RNA -> informational molecule Genetic Code o Codon : mRNA Sequence of 3 bases in mRNA (triplet code) Each codon specifies one amino acid or it specifies punctuation (stop or start) Why not 1 to 1? Could only code for 4 amino acids! With 3 -> make all 20 Code Table o DIAGRAm -> know how to read o 3 stop; 1 start o mRNA is where codons are 2. Translation o Polypeptide synthesis o 1. mRNA associates with ribosomes o 2. Amino acids to be incorporated into the polypeptide are carried by tRNA molecules o Changing from nucleic acids (DNA, RNA) to proteins o Ribosomes are machines that make protein synthesis work o tRNA -> carriers of nucleotides tRNA o Very shapely and loopy o Lots of H bonds (internal complementary base pairing within the single RNA strand) o Loop 2 is the most important: has the anticodon o Anticodon is complementary to codon of mRNA o Anticodon: 3 bases complementary to the 3 bases of mRNA codon (loop 2) o Amino acid attachment site : at 3’ end of the tRNA molecule o 3’ --- AAG --- 5’ (anticodon in tRNA) o What is complementary codon?
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Biology Exam1 chapter 13 - Lecture#14 Chapter 13 Chapter 13...

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