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Transcript
How Genes Work Genes on DNA are used to make RNA Transcription RNA is used to make proteins Translation © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 1 Information Flow Transcription In Translation In the nucleus the cytoplasm Animation © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 2 RNA vs. DNA Both are linear nucleotide polymers RNA differs from DNA Single stranded Ribose instead of deoxyribose U base instead of T © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 3 Three Types of RNA Messenger RNA (mRNA) Encodes Transfer RNA (tRNA) Aids proteins translation Ribosomal RNA (rRNA) Used to make ribosomes © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 4 Transcription DNA information is copied into RNA Similar to replication with three differences: RNA polymerase is used instead of DNA polymerase Only genes are transcribed not the entire genome RNA is made instead of DNA © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 5 Transcription RNA polymerase starts at promoter Its complex unwinds DNA It copies bases using complimentary base pairing (U v.s. T) Moves down one strand Stops at terminator © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 6 Introns & Exons Eukaryotic cells have non-coding regions in genes (introns) Removed after transcription Exons are connected to produce the mature mRNA © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 7 The Genetic Code Translation of RNA 3 bases = 1 codon 1 codon = 1 amino acid © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 8 The Genetic Code Possible codons: 4 X 4 X 4 = 64 20 possible amino acids Most amino acids have more than 1 codon Degeneracy of the code Why many mutations are silent (make no protein change) Three codons code for no amino acid STOP codons © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 9 Translation RNA sequence translated into protein sequence Genetic code used like a dictionary Ribosome Holds mRNA Links amino acids together © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 10 tRNA Two binding sites: Amino acid site Anticodon Amino Acid Serine Amino Acid attachment site tRNA Matches the Amino acid with codon Anticodon Codon mRNA © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 11 Translation Ribosome holds mRNA tRNA binds to first codon AUG – start codon = methionine Second tRNA binds to next codon Amino acids are linked Move to next codon Animation © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 12 From Gene to Phenotype Genes are inherited as DNA DNA is transcribed into RNA RNA is translated into protein Proteins give the organism traits Mutations in DNA produce changes in traits © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 13 Sickle Cell Anemia Gene for hemoglobin One base pair change Causes one amino acid change Sickle Cell phenotype © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 14 Process Animation 13.1 The Flow of Genetic Information in a Eukaryotic Cell Macintosh Windows © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 15 Process Animation 13.3 Translation Macintosh Windows © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 16